Sorry for my bad english, i am only 14.
Now players can use strange signs like: §, arrows. IMO this is hard to write. On server is griefer hes nick is mayby...§rit+-8,4rmfmf . I think "/votekick!" and... writing §=+-wafasfas,?[sfa is very hard. My suggestion is restriction this to latin alphabet and numbers. [A-Z];[1-9]