When an account is deleted, posts made by that account _on the main site_ with a negative score are deleted along with the account. Previously all negatively scored posts _on the meta site_ were also deleted, but [this behaviour changed very recently](http://meta.stackexchange.com/a/278218) and now all meta posts are preserved.  All comments are preserved, although like posts they there are "anonymised" and are attributed to "user#####".

(For completeness, there is a stronger form of account deletion, called _destruction_, which will delete _all_ contributions by the account. This form is generally reserved for spammers and users trolling the site, and additionally feeds into a system designed to prevent those users from posting again.)