Is this honestly really necessary? I mean, isn't it much easier to just call them "Fighter", "BM", "Thief", etc.? Besides, newbies to the forums would get confused...

Newbieboy001: Who's "Karn"?
Veteranman345: lol He is the Fighter. We call him Karn. Silly newbie! lolol!

Chaos would ensue... Chaos I tells ya!

EDIT: *remembers he likes the chaos* I shall suggest "Karn", then.