Fediverse

It's mostly to maintain the structure of a comment tree in my best guess. It'd be strange if a comment under your comment just bumped up the tree to being a reply to the person you were replying to.

Continuing to show your username on the deleted comment is a UX design choice that I understand and sympathise with questioning but it's kind of irrelevant when you think about how ActivityPub and the Fediverse works.

Basically, even if Lemmy did hide your username, any ActivityPub server connected to any instance connected to your instance will have received that comment and you clicking "delete" is basically just asking everyone (possibly hundreds of servers) to please delete it. A server lagging behind on syncronisation, a server modified to discard delete requests (maybe for archival purposes) or even one that just pretends to delete comments for malicious purposes will still have that data

I guess a TL;DR would be that it's a UX choice but kind of an ant hill compared to the mountain that is the Fediverse. It's not a bad thing but it's definitely a trade off you should keep in mind

Also your upvotes and downvotes are also public