What happens to very good answers from removed users? Do they get deleted?
In particular, I'm worried about user with over $100$ answers and over $10000$ rep.
I think they should be protected if not already.
When an account is deleted, all negatively scored posts are deleted. However StackExchange employs only "soft deletion" which means that these posts still exist, they are just hidden to users without sufficient privileges. Such posts can be restored (if you can direct moderators or other sufficiently privileged users to their location for undeletion).
(The undeleted posts are anonymized, meaning that the original user name is no longer associated with them, but rather some
user#####, reflecting the user ID of the account. Though not quite as simple as before there are ways to find such posts.)