Link to Mod (http://custom.simplemachines.org/mods/index.php?mod=3113)
This mod allows users to ban themselves from the forum.
A new permission needs to be granted in order to allow users to use the new function: Allow members to ban his own account, in the Member Profiles section.
Once allowed to use the function each member will find a new menu item in their profile page. There it will be possible to specify the reason for the ban, the length (in days), and the type of restriction: post and/or login.