On reddit if you have a low karma your account gets severely limited. Shadow bans, you can't post on many subreddits etc.

But there's no such issues here most of the time. Each post / comment stands by its own merit.

I'm not sure but maybe it's because reddit is aggressively banning or shadow banning accounts.

Every week spez does something to mess it up. It's hard to keep track.

You have to modify lemmy or piefed code to not delete the post from server instances upon request. It happens automatically.

The comments stay and can be viewed on your profile. But they cannot be discovered by others because the post which reveals them to the outside world is gone.

Comments work a bit differently. When you look at a post, and a comment is deleted you can still see its reply comments.

So post is always the starting point of discovery. If you delete that everything inside is effectively gone—like removing the only door into a room.

Hope that made sense.

Who decides what is "truly horrible?

Exactly. A community rule violation is what I had in mind. Some things universally "horrible" I can think of are hate speech, racism, and bullying etc.

Yes. But by default the instances delete the content when the request comes.

Clients like voyager and summit do show your comment because the reference exist on your profile but others cannot discover it because the post itself is gone from all feeds.