Well, if your posts reach other Lemmy instances, those don’t need to delete them just because you ask them to…

Post so lame get downvoted even after deletion

I would guess the deletion hasn’t propagated to all server instances so it’s still showing up in those instances. I imagine that posts are truly deleted but just marked as such I the database. Therefore a down vote could still be attached to the now deleted post this incrementing the counter.

The good news is karma isn’t a thing here so don’t worry about getting extra down votes.

you can up/downvote deleted posts, even if you can’t read them.

The Internet never forgets.

Federation is spotty

It may be gone where you post it, but might still be visible from a different instance

It can take a while to have the deletion request propagate to every instance that duplicated it. And then there is no guarantee they honor the request, if they ever even receive it.

It’d be a good idea to get into the habit of assuming any thing you post will be around forever.

On my UI deleted comments show up as empty comments that say [deleted] and you can see who wrote it. I’m guessing people downvote deleted comments out of spite because they’re annoying.

Also, weirdos will check what your comment used to say and reply to it anyway. I hate when they do that.

Edit: Now I see that you are talking about posts, not comments. Disregard.

There’s a place in settings where you can hide down votes.