k.
when using MQ's who, it uses the same options as /target, or ${Spawn[search]}, or /maphide, etc.
The options arent 100% the same as EQ's /who. So, /who "guildname" isnt going to be recognized as a guild name, but /who guild "guildname" should. I honestly couldnt tell you if it works right for guild names with spaces in them

some guilds also have spaces BEFORE their name. heh.
if you use EQ's who, which is / or if you're doing /who all, you can do it the EQ way...
/ <guildname>