I had this bug recently on beta 40 where I would reply to a comment on a post and my comment would show up. Then if I refreshed the post to load in new comments, my reply would be collapsed and clicking on it would lead to a 'no comments added' message. The comment would still be visible in the profile section and from other lemmy apps.
Edit : some photos as proof/example
Edit : This is not only an issue for my comments only, it is also issue for comments from other people aswell. Usually it seems to be an issue associated with the last comment of a thread where the these comments are collapsed in sync and when I expand them, no comments are added. But these actually exist and can be seen from other apps(voyager in my case). Oddly this does not happen for every comment thread but it happens with enough comments that it is noticable. I have not been able dig up any other commonilities between the disappearring comments other than the fact they appear at the end of comment chains/threads.
Device information
Sync version: v23.08.31-14:10
Sync flavor: googlePlay
View type: Slides
Device: hanoip
Model: motorola moto g(60)
Android: 12
Just tried on your instance and it's working fine too.
You haven't accidentally set some filters have you?
No filters set as far as I am aware. I will try to link a video of the issue if possible.
https://files.catbox.moe/zzxj8q.mp4
Video showing the bug