In other words, are you saying that the whole protocol is being designed so that the distribution of respect will always be an entirely subjective function whose only role is to represent the belief of the community?

Yes. Valuation is always subjective. The amount of respect one has in real life is also the belief of one's community.

Suppose you happen to be in a group of 6 people where 3 of them rank themselves as L6 contributors. That means that only 3 people out of 6 are surely trying to measure the system impartially.

I disagree. It's possible that all 3 people are genuine and just have different views on what's needed.

the 2 players who missed the L6 spot will rank themselves as L5

Yes, of course. What's wrong?
Also, sometimes it's the opposite - many people are scared to advocate for themselves because they are scared of getting a reputation for being selfish, so I often explicitly encourage people to advocate for their own contributions if they genuinely believe it's the most valuable.

What do you end up with? I'll tell you: Pure noise.

It's a noisy measurement, for sure, but I believe there's a valuable signal embedded in it that tends to become clearer over time, and also as the number of rounds increases.

What do you think about the noise of subsequent rounds?