@slidey - I'm really sorry a thread has over run your notifications. It’s happened to me a LOT also. The only way to get away from it is to use the bookmark suggestion like @Lim has suggested it. There is unfortunately no ‘unfollow’ option for individual threads at this time but it is something the King team is aware of and looking into.
Now I go back to Diamond Diaries Community as I always help Diamond Diaries players to solve any questions. And I haven't playing Candy Crush Friends Saga and haven't helping players on Candy Crush Friends Community (except the player mention/tag me to ask trouble question, I will check any questions to answer if I can solve it. )
To add to what everyone here wrote someone asked once if they could just shut off a specific message and that's not possible. For notifications if you shut it off then you lose all other notifications. There is no way to just shut off one specific message.