How to remove your Reddit account
Deletion somehow does not work in certain languages other than English (bug). So, if the removal is not confirmed, go to preferences and switch to English as the interface language.
Direct removal link: http://www.reddit.com/prefs/delete/
Helpful Trick: Removing online data
Helpful Trick: Remove third-party logins
If you signed up for Reddit using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Reddit. Click here to find out how.