Trident: I don't think it is an issue of right or authority or that being a more or less accomplished performer determines if you can comment. For me, it's the issue of explaining the reason for your like/dislike or why you believe something is incorrect.

I agree with you completely that people like to be adorned. If I don't like someones singing, or don't care for a particular style of playing and have nothing constructive/specific to say about it, I don't. If I have something to add that I think would improve the performance from my perspective/opinion, I will. IMHO.