My opinion:
I refrained from using a signature on Stack Overflow like I do on The Code Project et al simply because (a) it's redundant with the auto-signature and user page, and (b) almost no one else does it, including the site's founders and noted author contributors et al.
Contrary to some opinions, I do indeed 'have a life', but I am very careful about presenting a professional and consistent presence on the web. Remembering that I am a guest on Stack Overflow, I wondered what the netiquette was, which is one of the reasons that I asked this question.
Another reason I asked this question is to see if anyone else cared about it. This is debatable - we have one 'get a life' with several downvotes, quite a few upvotes for 'no signatures', one vote for 'signatures are OK', and two people bothered to express an opinion. I would say that based on this the Stack Overflow community in general really doesn't care about signatures.
Thanks to all who participated, I am marking this question 'closed'.
Best regards,
Steven A. Lowe
Founder and CEO, Innovator LLC
www.nov8r.com