This happened to me once. What I think happened to me was that my post made it into the 'Top Comments' list which was on the right hand side of every page on their site. I also noticed that suddenly I had about 900 back links in about a week all from different pages on this site.
I wouldn't worry about it too much. It's not like you are doing anything black hat yourself.
I would just keep building other normal links as well...ideally high quality links.

Had the same thing happen congrats on getting one of the coveted top slots enjoy it. No harm should come as it is, technically speaking, "all natural"

This happens quite often if you use blog commenting for SEO purposes. Often a comment will be made which goes onto the sidebar as something like "recently commented..." etc and then that goes on every poge so you end up getting a link from all the pages on the site.

What will happen is you'll get that link initially but then when Google re-scans the website it'll see that the link is no longer there. (Your original link will be though of course)

Agree with the above posters, one of you comments made it to the sidebar, which is probably on every page of the site, so you're getting one link per page...............keep it up