You know what they say about assumptions...

Fun fact: George Takei himself complained that Sulu is portrait gay in the new movies. He said that even tho he himself is gay, he always played Sulu as a straight guy. But why would the headcanon of an actor be more important than any other
- I mean, if it informs the performance meaningfully, it's part of the end product. Doesn't mean it's necessarily canon or whatever, but it certainly has the potential to impact later performances if direction moves away from the actor's previous internal preparation.
  I could see it being off-putting to work under a director or with writing that bleeds your public personality into your role, especially if it's one you've gotten to a certain place with.
  Like even as a roleplayer, any character i might embody in the moment has a life of its own that's distinct from mine, and would make decisions that I wouldn't. If someone tried to push me into acting a way that's more typical of myself out of character or that's more in line with a different character I play, or if they reacted to the character based on that outside stuff, I'd certainly resist it.
  
  True, I totally see your point. I think there are different ways to see this:
  First, it's someone else who played it so he wasn't forced to do anything. It's just a role he played and now someone else does with different interpretations. You wouldn't blame a Hamlett actor for performing differently than their predecessor. Sure, it's different since Sulu was brought into existence by Takei and didn't really exist in a book or something but still a fictional character played by different people.
  Since it's just one little scene I didn't even remember after the first time watching, it isn't part of his story or character building or something. He is just greeted by his husband (or partner) and daughter. In my eyes more of a homage or easter egg to Takei than forcing his personality into the character.
  Lastly, HolLyWood goNe w0ke aNywAyS. I don't mean this negatively obviously. Media puts diversity into more and more places and it doesn't even have to do with Takei himself.
  Even tho I started the last paragraph with lastly, let me add that I think it might even have more to do with losing control of your creation. Sure, Sulu started as the character played by Sulu but he developed further. It's like trying to force the genie back into the bottle. Sulu isn't Takei and Takei isn't entitled to control Sulu.
- To be fair, John Cho played Sulu straight until it was revealed that he was gay. And even then, there wasn't much gayness to his acting. Unless you count bringing a sword to a skydiving phaser fight, but I'd consider that more bad ass than gay.
  
  And even then, there wasn’t much gayness to his acting.
  Care to elaborate?
  
  Isn't there a scene where he means his husband?
- It's not just how Takei played it, the first thing an inhibition-free Zulu does in The Naked Time is to go after Uhura - and Mirror Zulu obviously has the hots for her too.
  
  Takei's Sulu always gave me bisexual energy.
  Source: my wishful thinking (aka my ass)
- Why wouldn't the original actor be the authority on the subject? If they immersed themselves in the material and have a good memory, wouldn't that be "the truth"?
  
  Why wouldn’t the original actor be the authority on the subject?
  Careful. Would you say the same thing about Jared Leto and his characters? Or
  <insert actor you hate>
  about
  <character they played>
  ?
- But why would the headcanon of an actor be more important than any other
  Idk perhaps because actors can imbue characters with unwritten properties through their portrayal?
  
  But only the first actor?
- George only came publicly out as gay in 2005...
  
  Which is still before the 2009 movie ...

With the debatable exception of Jadzia, all those characters were exclusively shown in heterosexual relationships.
Rejoined was a great episode.
- all those characters were exclusively shown in heterosexual relationships.
  That's not exactly evidence against them all being bi
  
  This is where the wishful thinking, mentioned earlier, comes to play I guess.
  
  By that logic, there's also no evidence that god doesn't exist.
- Julian and Garak were clearly in a relationship. Just ask Garak.
- Don’t get baited
  I got suckered into arguing about this very topic some days ago, and only had my sexuality questioned when they ran out of arguments. Suffice it to say that there is plenty of wishful thinking involved
  
  there is plenty of wishful thinking
  It's so bizzare and unexpected that a meme about "headcannon" would inspire wishful thinking of all things WHY
- Not too sure what's debatable about Jadzia. Julian on the other hand... pretty debatable.
  
  While she kissed a girl, it was never portrayed as a lesbian relationship, rather the post reincarnation resumption of earlier straight marriage.
  Did Bashir ever pine after a guy? O’Brien doesn’t count.
- Sure, but that doesn't mean they were exclusively heterosexual.
  
  The definition of canon is that which is shown on screen.
- Odo and Laas linked.
  
  Linking isn’t inherently sexual, as was pretty clear from that episode.

Kira was a rebel at heart.
Bashir was in the "I've been genetically modified, which is illegal, so should I have kids?" camp, if I remember correctly.
Sisko loved his wife.
Odo was a gelatinous blob.
Jadzia was influenced by past multiple personalities, so she likely loved pans and pots.
O'Brien was a weeb. He only loved his waifu, the transporter room.
Jake was a reporter. He loved crawling into holes he shouldn't have been crawling into.
Quark was a businessman. He loved risky ventures.
- He only loved his waifu, the transporter room.
  Slight disagree, he only loved his waifu, constantly breaking systems.
  Miles "I can fix her" O'Brein
  
  Better.

Although it isn't really shown, Odo is nonbinary by definition isn't he?
- Gender: fluid
  
  This is what my brain meant, but I am enjoying some consumption.
- Not necessarily. It'd be for how he views himself. While the shapeshifters kinda' explore the concept in some episodes, it may be fair to assume they identify as they present, because they can literally present how they want.
  Granted, I could see Odo having some odd identity issues with presenting to please others or over duty to his job more than personal identity given his upbringing...
  Did they explore his gender identity in that episode(s) or did they leave it all allegory? Ugh it was so long ago... Maybe time for a rewatch.
  
  As far as I know, Odo is a masculine Shapeshafter. It also use the identity of the one who study him, it was his choice to be like that most of the time.
- He present male and has had relationships with women. But he can present any way he likes. And the founders maybe don't even have gender.. so not even binary.
  
  The founders dont even necessarily have a particular body. They may just reserve X amount of biomass on leaving the link.
  
  Eh, the ability to present any gender he likes isn't what it means to be nonbinary. Presumably anyone in the 24th century has that ability.
  
  He had a short relationship with another "male" changeling.
- What definition is that? Assigned nonbinary at birth? The fact that he could choose to present as nonbinary but presents as male is pretty telling, imo.

Quark is a straight white male, or my name isn't Jeremiah Paxton
- He's a straight green goblin.
  
  This is acceptable
- So what is your name?
  
  Tim

Agreed on all points except Garak, the simple tailor.
Anybody who misses how shamelessly he flirts with Julian needs their head-canon checked on.
- I always viewed Garak as uninterested in anything but intrigue. He was inherently non-sexual to me.

Isn't cis another word for straight?
I honestly don't know, just asking
- Cis refers to gender identity where as straight refers to their sexuality.
  
  Thanks, that makes sense
  
  This is like when you cool things down to such a low temperature that they start acting like they're super hot.
  It's similar in that they're both arbitrary linguistic distinctions that do not apply under most circumstances (and indeed barely capture the phenomenon in the first place), reveal holes in our understanding of reality that even experts are largely unprepared to deal with, and have no practical, usable effects or results (although I'd love to know what the gay equivalent of superconduction is - is "superfluid" a gender?)
- Well, trans as a root means across from, or on the other side of.
  Cis means on this side of. Both are from latin roots.
  When using it in gender discussions, it means someone that isn't trans, aka the gender normative, aka the folks that match in terms of inner and outer gender expression.
  Cisgender started out as a term back in the nineties, as a way to be able to refer to the majority that are gender normative with a simpler term when discussing transgender/transexual issues. As you can see, it is incredibly cumbersome to describe the cisgender people of the world without using cis. Pain in the ass when you're writing or talking about the subject. And the nineties are when that kind of discussion became more prevalent.
  There's also the fact that people have put unnecessary weight to the word "normal", and tend not to understand the word normative. Because of the way normal has been used for a very long time now, despite it really meaning something that's typical, any use of it implies that everything else is abnormal in a bad way rather than just not typical. Largely because in most fields, abnormal is a bad thing. Abnormal blood work as an example.
  So, we have heteronormative and cisnormative for the straights and non trans people behaving in typical ways for those groups as well as cisgender meaning aligning with one's nominative gender.
  Now, can cis be used to denote "straight" people? Kinda, but not really. It would be a very unusual usage because straight in terms of non normative sexuality being discussed almost always refers to sexual orientation. Using cis to mean straight isn't unreasonable, particularly since you'll run into situations where gay people and trans people might just use straight as a shorter word for cis-hetero. But you won't see that in anything but casual settings because of the very confusion you're dealing with. Most of my close friends are gay or otherwise under the lgbtq+ heading, and I've never actually heard anyone use cis as a synonym for straight, but I have heard "straights" used as a term that includes cis.
  Yay for language!
  
  Interesting and still confusing haha.
  Thank you for taking the time, I learned a little today.
- i think he's assuming there's a difference between cis and straight but is too gay to know for sure
  
  Don't try to insult people just for asking a question.

Nog is straight. But also an incel.
- He also grows out of it, at least in The Visitor

Ah yes gender politics, only thing missing from Star Trek themed discussion.
- Naw it's not missing. Always been there.
- wym missing

Everyone knows...when you make an assumption...

This is wishful thinking. It was made within a heteronormative society, and most characters who have love interests and relationship histories are hence straight.
Unless stated or shown it's far more of a head cannon to assume a queer identity where none is suggested.
No media can fully escape the culture, period, and context it was created in.