Here are two trappings I've seen recently:
#1: Validating the right answer the moment you hear it, thereby short-circuiting any dialogue about the problem.
Recently, I heard a college instructor say, "I agree with you," anytime a student said something correct, and "Are there any other ideas?" anytime a student said something incorrect. My sense was that the phrases "I agree with you," and "Are there any other ideas?" were honest attempts by the instructor NOT to say "That's correct" and "That's incorrect". I caught on to this pattern of talk quickly, and I imagined students would catch on within a few days or weeks.
#2: Requesting that a nearly correct student "say more" in a manner that implies, "Could you please restate what you said using the correct terminology?" rather than, "I'm really interested in your idea, please say more about that?"
This can be subtle, as it often has to do with tone of voice, body language, and subtle phrasings. When an instructor does this, however it really gums up the dialogue. Because students pick up on the fact that it's not about their ideas, this kind talk quickly descends into a game of "the teacher is thinking of a number between 0 and 100." Students either start opting out or just trying to guess what the instructor wants them to say.
The Big Picture
Facilitating discussions is hard work. In my mind, the number one priority is getting students to invite me in to their learning through their talk. Largely, this means that they are sharing their ideas and thinking, not trying to guess what's in my mind or avoid being wrong. When I see instructors falling into these kinds of traps, I see this priority being undermined.
Some people might think the solution to trap #1 is to have a better poker face–don't have any "tells" that give away the right answer. I think that approach is flawed because it's trying to stop the symptom, but not the cause. I don't need a poker face if I am not listening to student ideas primarily through a lens of correct and incorrect.
Some people might think the solution to trap #2 is to not care about terminology. While that's possible, I don't think it's realistic. I think the solution is to distinguish the activities of "shopping for ideas" and "connecting with disciplinary formalism". The problem is in trying to do both at the same time and in the same way.
I certainly enjoy watching other people teach, because it gives me an opportunity to reflect on my own teaching. There are times when I "gum up the dialogue" and focus on correctness when I shouldn't. Sometimes by watching others, I understand better why we all fall into these traps and what impact it can have on students.