So vicious mockery is, to my understanding, the bard insulting a target, and the target taking psychic damage, and gaining disadvantage.
The flavor, as I understand it, is that they're so insulted it actually hurts.
Which lead me to wonder – could a bard get a vicious mockery off, and the target not know they've been attacked?
Of course, the target knows they've been viciously insulted, and assuming they fail their Wisdom check, are mad at the bard and would probably like to murder said bard. But, if they're all in a bar, and the target wants to attack the bard (attempting to murder him in broad daylight), it seems reasonable that other people would want to stop said murder – after all, it is just a bard insulting someone, and bards do that all the time – it doesn't quite rise to the level of trying to knock his lights out. (Although most of the patrons of said bar are probably fairly understanding of his position…)
To look at a slightly different situation, if a wizard cast fireball on a patron, the entire bar would be up in arms attempting to lynch said wizard. Would there be a similar effect on a bard mocking someone?
So I guess my question boils down to: Do other people recognize vicious mockery as an actual attack, or do they simply think it's a devastating insult?