Thanks very much for clarifying Emberguard and for the advice.
I know that you can use Emoji's in the game, but to be honest I'm always weary of doing this because, as Selene mentioned, some PC users can't see some emoji's. What I thought Selene maybe meant was a automatic big coloured symbol on the left hand side of each guild message (eg. a big red circle or something), but I see your point, this can probably be closely mimicked with emojis.
Regarding using text to differentiate, we already do this in our guild, it does help a little, but I was thinking that a different colour background would be a bit more effective.
I haven't considered using symbol emojis as Selene suggested, I might give this a try and see if it works for everyone. Thanks again
(PS. Love the song <3)