Whether the 'performance' enhances or distracts from the 'music' seems, to me, to depend on the levels of engagement the musician has with the music, on one hand, and with the 'context' (audience, type of occasion, cultural location etc) on the other. Sometimes hamming it up is 'the go' and it works; if you mistake the situation it has all the appeal of a bottled fart. There seems to be some behaviours that are traditionally associated with some instruments ('the faraway look on the face of the melodeon player' gets a mention in SHirley Andrews' book on Oz colonial dancing "Take your partners") and other behaviours seem associated with some contexts; woe betide those who applaud at the end of the first movement in a symphony, for example.

When my daughters are watching music videos and comment on the music, like BillD, I suggest they listen with their eyes shut to test whether the appeal lies in what they hear or what they see. Or whether both senses are required for a full appreciation.

But most people seem to be able to tell, and approve, when the engagements are appropriate.

Cheers, Rowan