There is a link to the left under "my boards" that says "Unblock Nesties" - you can click this to unblock someone at anytime.
If you block the original poster of a thread, you'll still see their subject line because we want to let you know there are replies in there (it would be weird to block all the replies from you too). But when you click on the post you won't have to see the blocked member's post(s). Also, if another member quotes someone on your block list, you'll end up seeing what they posted. (For anyone who didn't see the earlier announcement and has no idea what I'm talking about, we've added a block feature).
PS - I noticed a lot of people also asking about our search function. We've made updates to this as well. Just enter the topic you are searching for in the nest tab at the top of any page and results will be sorted by articles, blog posts and message board posts.