Ah, a vote in favour of strife. Yes, that's what it is.

Nope, that's what it is not.

That specific comment is really not about LW voting system at all, it's about people's ability to take criticism (of various sorts including totally unfair one) and the usefulness of such an ability.

What to promote? Harmony, or strife?

Still nope, even in the context of LW karma that's the wrong framework. Negative feedback is not strife -- if you screwed up and no one will tell you so because it's not nice, you will continue to screw up until reality delivers the message to you. Feedback and consequences is a much more useful set of terms to use.

It's the attitude that begets disapproval

LOL. Would you like to... adjust my attitude? X-D

the belief that the dignified way to deal with mean-spirited criticism is never to internalise it; presumably to have / express a low opinion on the criticiser right back?

You're missing a very important part: distinguishing between the criticism of an idea or a proposal, and the criticism of a person.

You should listen and pay attention to the criticism of your ideas. You should not interpret the criticism of your ideas as criticism of your self/identity/personality/soul/etc.