Originally Posted by ptjackson
Not sure why but I'm not sure how much it helps I think "domain uniqueness" matters for back links for SEO
It really comes down to Google's view of the source site. Assuming his post wasn't on one of the black hat forums or a known pay-for-links site, I don't think there's much need for punitive concern. Recent comments/Top Comments/Blog Rolls can create these multiple backlinks, and Search recognizes and accounts for this, with it being viewed as a single link a very strong possibility.
As an example, ptjackson, your site is becoming an authority site for the lawn and landscape industry. If you had a "Landscaper of the Month" and a link to their business injected into every page, that landscaper would not likely find himself on the wrong side of Google's temper.