I frequently find this, for some reason kbin.social comments aren't federating properly. When they reply to my comment thread I am unable to reply to them, and when I log into kbin.social directly and post there my comment doesn't show up on lemm.eefor some time at all.
Edit: A good fix is to apply a language to your comment, eg English. This should allow your comment to post. However it seems like there is still some issue with comments federating across after that - your comment might appear on kbin, but you might not get their replies again.
It's a difficult one. There are ongoing federation issues just about everywhere even within Lemmy and Kbin themselves, so once we get to talking cross-compatibility the problem appears to be even worse.
It has got drastically better since I first joined, so there are clearly investigations underway, but there's still a fair way to go until it's totally reliable.
That said, just to clarify, when you say you're "unable to reply to them" do you mean because their comment doesn't show up on your side, or because you get some kind of error or other weird behaviour when you try to reply?
That said, just to clarify, when you say you’re “unable to reply to them” do you mean because their comment doesn’t show up on your side, or because you get some kind of error or other weird behaviour when you try to reply?
Their comment is there (at least some of them are) but I cannot reply. My comment doesn't enter in, I just get a spinning wheel, with the text box effectively switched to Preview mode. I don't think it even times out, it just keeps spinning until I close the page or hit Cancel.
If I then log in directly to kbin I can reply to them there (and I also sometimes see other kbin comments that aren't on lemm.ee), however back at lemm.ee my new comment isn't there. I haven't gone back to check any of these replies later, I imagine they show up on lemm.ee eventually, but have no idea how long that takes.
Next time the spinny wheel thing happens, try selecting a comment language from the dropdown. I've noticed that sometimes (especially when replying to an external thing from Kbin or Mastodon, but also sometimes from Lemmy so god knows) it won't let me post without explicitly setting the language.
Very much a workaround rather than a fix but it might be easier for you than logging over. Assuming it works, of course, and your problem isn't something totally different!
When they reply to my comment thread I am unable to reply to them
AFAIK this is due to most (or all?) kbin users limiting what language you're allowed to reply in. Try setting your comment language to "English", then it should go through (Edit: I see you already got this advice from @thegiddystitcher as well).
when I log into kbin.social directly and post there my comment doesn’t show up on lemm.ee for some time.
Not much we can do about this - your comment shows up on lemm.ee as soon as kbin.social sends it over.