hey Lisa,
You're making me hungry! Where can I get these sugar cookies???
I think the blog post I read wasn't about leaving a "spammy" signature but was just about being involved in SEO. It's the thing about natural vs "artificial" links, and if you are on a seo forum, your site will be "flagged" as being "seo'ed". I think it's a bit paranoid, but raises the question of how google views "non-natural" links... i.e. anything that isn't randomly given by someone who doesn't know you.