I noticed that some people have signature links in bold text. Is this a visual/style thing or do bold backlinks mean better SEO?
Bold text is basically emphasized text and if used correctly can add more weight to specific keywords. For signature links, the best thing to do is write a descriptive piece of text. Include your anchor link keywords within that, and that will place a stronger relevence on your keywords. Any surrounding text to your contextual links adds a themed relevency to them. If that makes sense?! ie - A Wide Range Of Promotional Products - Get Quotes on Pens, Mugs, Mouse Mats & Other Business Gifts Andy
Bald is favorable, but the signature links are much more important for driving traffic than for SEO purposes. So yes, make sure they're descriptive.
nobody actually knows whether this is true or not, people surmise these things. I personally think that link relevance is more likely computed from pagenames and titles than from surrounding text. anchor text links on an otherwise empty page still work just fine.