If you do not know about special characters :
Special Character: A character that is not a letter, number, symbol, or punctuation mark. Control characters, for example, are special characters, as are special formatting characters such as paragraph marks.
Like this: http://copypastecharacter.com/all-characters
Well, what do you think about those symbol and special characters in nicknames, guilds or parties? I really think it is visual polution and also… well, you might know what happens whenever you try to whisper that friend of yours that his nickname is something like [-xXx***D@rk***xXx-] or e$p&rM@g!cian or whatever is.
Seriously, why you try to write your nickname like this? :v