If you are using firefox, just "hightlight" the particular anchor text, right click and view selection source. If you can't find the NoFollow tag, then it is DoFollow.
I wrote an article about that on my SEO blog. It links to a script that you can drag to your favorites and check for nofollow in IE or Firefox. Check for nofollow
To make things simple, you can always add SEO for Firefox add on into your Firefox browser. This simple add on will simply highlight links that are nofollow. Thus, after commenting or there are already comments in place, you can verify the dofollow status with a glance. Enjoy.
Here's the absolute easiest and most effective way of determining it (if you use Firefox) - just download Stylish and add the code on this page to it.