Using this query get post list of a deleted user or answers of a deleted user and estimated reputation of a deleted user I could realize that an specific no longer user had 722 answers and approximately 28753 points! and yet decided to delete their account.
It's not the first time that I witness such incredibly deletions. Another user whom had his real name, (I know because I once had a discussion with him and that's how I could link his name) he had approximately 24799 points and 584 answers.
I think we should do something about it because you don't get easily more than 20k nor you easily answer more than 500 answers. Takes a lot of time, effort, etc.
I have thought in this:
To have something like "Please think twice, it's very likely that you'll regret" additionally to the default one day to wait for the deletion.
If the first doesn't work, then at least we should do something about it with their points. We could suggest the user that had decided to delete their account to spend their rep in bounties to difficult questions or questions that the user likes or in outstanding answers.