I like to think I can be decent even when not required to, even when it won't come back to me.
If the "real me" is a person who can perceive the difference between good and bad things, and also show a bit of decency about it, then yeah, I'd like that to be the "real me."
Feigning liking something to be polite doesn't make the thing good, and that doesn't mean anyone is an asshole either. Ugh.
Nah. If I were reviewing something without having been given the instruction "please be truthful, I need to make this perfect" or similar, I would default to encouraging the skill rather than trying to help perfect the output. In doing so I would overlook minor issues that will iron out with experience across multiple works.
If the person was submitting the result to a competition or something and asked my opinion on that specific work, then my approach would be different. Not cruel and hurtful, course not, I'd just mention things that would otherwise be annoying and petty to bring up.
In the case of pre-sapient AI, it won't hurt (and may even be helpful to the relevant dev) to point out where it's tripping over into uncanny valley. There's no benefit to encouragement in this situation as it's not learning a skill, it is trying to replicate the output of one.
I remain convinced, struggling to complain about the quality of the song in unflattering terms is vacuous commenting. I wonder why people want to do that at all.