I do that, but only if the post I'm replying to is the one directly above my own. Otherwise I always make sure to quote them to make sure there's no confusion 
If they're posting then that means they're following the thread, so naturally they'll get a notification for it regardless. And if they don't care enough about the thread to click on said notification if it isn't specifically mentioning them, then they had no interest in the thread in the first place and thus it's not worth interacting with them further
If they're posting then that means they're following the thread, so naturally they'll get a notification for it regardless. And if they don't care enough about the thread to click on said notification if it isn't specifically mentioning them, then they had no interest in the thread in the first place and thus it's not worth interacting with them further