I may be being thick, but if I am reading a Thread is there a link to Create New Thread on that page?
The only one (I've found) is on the Thread Index page, rather than the Thread Read page.
I'm just thinking that on old forum we used to get people tagging new thread material onto an existing thread rather than starting a new thread ... and a "New Thread" button, everywhere!!, would perhaps prevent that?
I note that if I click on the Category Name and then NEW TOPIC from that index page, the new topic is pre-filled with that category name, which is good. Perhaps if I was reading a, say, SQL 2014 thread and starts a new thread that should default to SQL 2014 too? (Could also be that having Category BLANK but forcing user to choose one might be more accurate)