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.ee for 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.
By the way, do you remember any specific comment where this occured? I would love to do some testing if you can link a comment like this.
I’ve just tried to do a mention to myself from my kbin to the comments. That should give me a lemm.ee link to the threads.
In the meantime, I did dig up this one though:
Here I was able to reply to the same comment the kbin user did, as well as in other places on this post, with my lemm.ee account. However I could not reply to the kbin comment linked. I replied to him in kbin, however if you click the federated link on his comment it only displays that comment alone - kbin doesn’t have context nor does it display replies to individual comments. In the full comments my reply is there though, along with my lemm.ee replies.
It also looks like my previous kbin reply has not federated into lemm.ee, after more than 2 days. My guess is the mentions won’t work, either - they haven’t come in yet in the last 15 min. I was able to post just now by applying the English language, though, but my deletion has not federated to kbin. My subsequent reply to this test comment from kbin also hasn’t come through on lemm.ee
Here’s the kbin link to the full comment thread. Like I say, individual comment links are kind of useless on kbin, so you’re better off searching for the posts/usernames manually on the page.
It’s not limited to lemmy.world posts, either. Other problem kbin comments were on lemmy.fmhy.ml and lemmy.dbzer0.com.