Watching threads you create and threads you reply to should be separate settings. The checkbox in my account settings combines them into "Automatically watch threads that you create or when you reply".

I always want to watch threads I create, but usually don't want to watch threads I reply to (er...to which I reply).

 

I suggested a similar idea in this thread:
http://forum.allaboutcircuits.com/t...ifications-only-for-threads-i-started.106757/