This brings back the ability to Ignore Threads, but also:
You can ignore an entire board on PD.
You can ignore threads based on their tags (though I don't think that will work well here, the option is there if you want to experiment).
You can choose to ignore threads based upon whether or not a member on your ignore list in involved. (Without testing it, I'm not sure if they mean only when an ignored member STARTS the thread, or if it only takes that person POSTING in the thread to cause it to become an ignored thread).
You can review and manage all of your ignore options from your UserCP.