That noise was not microphone feedback.
It was a series of distinct tones. It was intentional, but I'm sure whatever contractor sold the technology to the network promised it would be inaudible.
I'm not sure if it's some kind of audio watermark or timecode, but I think it has something to do with synching the live feed.
It was definitely not feedback though.
This article is a list of reasons why it is rude not to drink, especially the one you highlighted. There is a tacit agreement that we are all going to get drunk together, and no one likes Mr. Judgy sitting sober in the corner observing all of our drunken flaws.