People do NOT have them in their signature. It just may look like it on some threads because for example maybe they have a middleman thread and to show how trustworthy they are they show all of their vouches. All they do is put a little line like this ____ and insert their vouches below. It is not their signature. Your vouches can eather go into your profile where your vouches should be or you can put your vouches on a deserted thread you made long ago. Hope this helps.