In my opinion:
Some possible things can do it:
-Use 16+ character name(and glitch into invisible)
-Hack the 16+ character name
-One admin joke with you(with script?)
-Some non-ascii charaters in his/her name
-Some other things,that I don't really know how it works. :')
Related google search words(I can't post links):
-ace of spades client emu => then click on mpgh.net related link.
<it's for aos75/classic,not OS or Steam_AoS, have fun with it!>