As mentioned above, it's not possible to do so at the moment.
The best way to choose which threads appear is to automatically subscribe to any thread you post in. You can set it to no notifications anyway so at least you won't get bombarded with emails. Then, if you no longer need a thread to be displayed, you can simply unsubscribe from the thread.
This method also helps when the search function goes offline as you'll still have access to all subscribed threads
Sent from my HTC One via XDA Premium 4