Oh yeah they are. I have uneddit which will show deleted or "shadowdeleted" comments. Similar to shadow banning where the person banned doesn't realize it, the mods of that sub are known for deleting comments and the original commenter won't know it because it will still show up in their overview. They only seem to do this in threads with a lot of fat hate. I made a discussion post about this a while back when I noticed it in another sub with one of my own comments.  https://voat.co/v/fphdiscussion/comments/611709