When I created my 2nd character yesterday, I discovered that I was automatically in the guild my 1st character had joined!!
I had previously noticed that my guild membership was under my account name, not my player's name. But it allows you to change the displayed name so they recognize you when they see you in the game.
But guild membership should be attached to the character ... not the account.
If my fighter joins a guild my other characters should not automatically belong to that guild. Each character should have their own guilds memberships.
If I wanted a Signature I would have a Signature --- but i don't want one so I don't have one.