Maybe I'm just lucky, but I've never actually experienced any loud/boorish behaviour in an airline lounge (MLL or otherwise). The only sort of potentially offensive lounge behaviour I've seen is guests taking their shoes off and resting their bare feet on a chair or ottoman. Maybe I've been in Asia too long, but out here, displaying the soles of your bare feet is considered highly offensive and it's just something I don't like seeing in a supposedly 'dignified' public space either. (It wouldn't bother me if they had socks on or if it was in a designated sleep/rest area where they were covered in a blanket).
Oh and please use the tongs not your hands when picking up food like nachos or veggie sticks!
In general though, an airline lounge is like any public space such as a restaurant, movie theater etc. There will always be people acting in a way that does not conform to the expected of the majority... that's life!
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I've never found Behaviour in the lounges any worse than on the airplane itself, though that's perhaps an unreasonable benchmark.