I've made 3 comments in the past 2 days but none of them show up if I look at the home instance of the communities they're on. They're all on lemmy.world, but I see comments from other instances in the threads so I don't think the problem is on their end.
edit: specific comments
https://discuss.tchncs.de/comment/6118062 vs https://lemmy.world/post/10292419
https://discuss.tchncs.de/comment/6117417 vs https://lemmy.world/post/10293966
https://discuss.tchncs.de/comment/6060083 vs https://lemmy.world/post/10220386
edit: seems to go back further than I thought, at least 3 days, and including other instances:
https://discuss.tchncs.de/comment/6058391 vs https://lemmy.blahaj.zone/post/7109033
https://discuss.tchncs.de/comment/6044803 vs https://lemmy.ml/post/9981184
edit: seems to have started working again on 1/6
I just checked, the last comment I made that got an upvote was 2 days ago on startrek.website. Aside from discuss.tchncs.de of course.