Yes, there is no way to know for sure unless someone reported the activity on the website to porkbun and somehow their identity had to be exposed, I don't even know if that's possible.
It's just highly unlikely, I could make the wording fit that, actually
(so no, this is just a slightly expensive joke by someone)
What do you base that assertion on? I don't see the name Microsoft anywhere, it's all anonymous. Sure, it could reasonably be them, but there's nothing on that site that would rule out a slightly expensive joke by someone.
I think you're misunderstanding, I'm of your same idea, I'm saying that it is not Microsoft, exactly because, as you say, it's all redacted and registered through porkbun, which isn't the registrar they usually use, I also couldn't see it as a covert operation sponsored by Microsoft because Codeberg is frankly no threat to them at all, so it wouldn't warrant spending any money on this publicity stunt (even though I personally support it against GitHub, but I'm just being realistic here)