Really nice post and very well put. I always appreciate feedback form my partners but sometimes it can go a little overboard. Generally I think that the "lecturer" is just so excited about what they have learned that they can't help trying to share it. They forget their place.
But what do you do if you see someone lecturing without qualification.
I let them have their say, usually tune them out, and then when they are done I go back to working on what the teacher told us to work on.
Its a great excercise in patience. And sensei will more than likely handle it if it needs to be handled.