Some accounts are deleting their posts after a few downvotes. It’s devastating on communities like c/asklemmy.
Lemmy doesn’t track an account’s karma like reddit. So, all downvotes will be isolated to your post or comment and won’t affect your account—unless you wrote something truly horrible.
Remember lemmy is a community effort. Deleting a post also removes all comments on it. So you are not only robbing the effort others put in, you are actively removing knowledge from the fediverse. Others won’t be able to find it through search and lemmy will seem lonelier than it already is.
Different strokes for different folks
Edit: plus, bad posts can have valuable comments. They frequently do, if the post is bad because of an error in logic or ethics that can be thoroughly explained/corrected for the poster and any lurkers who identified with the post.
Yes, I frequently learn things from the replies to comments which have been removed by a moderator. I also like to look up the posts themselves to learn what was objectionable.