Letters with symbols / lines through them...

First off, are these types of letters allowed for guild names, character names, and so on? Also, how do you make them, does anybody know? I want to join a guild that seems like a nice leveling guild, but the guild name has one of those letter O's with a line through it, and I don't want to get in trouble if I join it and the guild name gets reported or anything.

The guild name is VenOm with a line through O.

Thanks for answering.