MCBans/MCBans — pull request #28 by rakiru (2011-11-27 22:06:54+00:00)
Title: Block invalid player names for bans

...3 and 16 characters (inclusive) and composed of only alphanumeric characters and underscores

Take a look at how many bans there are for player "g"...
Simple regex to make sure players being banned are legal player names