What not to do during a class visit...

So I feel this is valuable to pass along...I assumed this would be common knowledge but this has happened more than once over the last few weeks.

When you are a visitor in a class do not raise your hand to participate...even worse don't blurt out comments. I have been shocked recently at how many people seem to feel this is acceptable behavior. Why this is poor form for a visitor:
1) usually the comments are rather weak especially in higher level electives where without completing previous courses or attending classes all quarter its tough to make relevant comments. Instead of impressing it often makes the visitor look foolish.
2) you aren't paying an obscene amount of money to participate.
3) you aren't getting graded on participating.
4) current students find it obnoxious...when we audit classes we typically don’t participate due to reason #3, unless specifically asked to answer a question by the professor.
5) its not uncommon for students to talk to student adcoms or even admissions people about egregious instances.

The ultimate example of this was a few days ago, we had 6 visitors in one of my classes. One visitor blurted out a comment and that opened the flood gates and more than half by the end of class had made comments or asked questions...not a single one of them were insightful and only one kid even bothered to raise his hand and the professor tried to ignore him but his hand just kept waving until the prof gave in. A student actually said something to a few visitors sitting near him about observing but not actively taking part...5 minutes later one of them just couldn’t help himself and made yet another comment. Unfortunately, the visitors did not know the student who hinted they should shut up is a student adcom and had a sit down meeting with the dean of admissions about the episode and the list of visitors for that class was reviewed.

I did not notice this last year but I have seen this on numerous occasion where visitors raise hands but then have to be informed by the professor that he does not allow visitors to participate in his class or ignored by the professor.