You mentioned that, users (abusers) just keep creating new accounts, and in the next section you said user retention is close to 0. Whoever comes here usually stays here, and tries hard to abuse it with many accounts(that might be the reason for retention statistics looks weird) at least that's what I've seen so far.

"every individual pursuing their own maximization" - including steem-ua, being closed source makes it questionable. (I wouldn't understand how it works by looking at its code but, it's a measure of trust.), but I guess you are trading this trust with monetization.

"Of course UA is now biased towards the Witnesses!" - indeed, and
""Follower Graph" is or is not a good signal to use at the core of UA. That's just an implementation detail, really..." - so how can I trust in you about what will be implemented next, after reaching some point?
Let's say when you reach 1M SP or 10M SP, you may offer alternative upvotes for higher delegators. What will minnows going to do when this happened, will you turn back and listen to them even it means far less earnings for steem-ua?

I do know nobody going to change how my car works out of nowhere, or if it's going to leave me in the lurch at some point just because he likes to ride on highway.
I do know my body will do whatever it did from the beginning of life.
We have years of experience and observations on these subjects but not on steem-ua.

They found a way to split the atom and used it for a nuclear bomb. ¯_(ツ)_/¯

One last question, did you ever consider comparing UA ranks with the Global Blacklist API
And would you mind sharing if there is anyone above 17406 (my poor ua rank.)
I might fill half of the utopian's blacklist. I'm just wondering how many of those accounts are worthy then me based on UA calculations.

And don't get me wrong, I keep commenting about steem-ua since it's pretty popular this week. I'm not against it or else, I appreciate your work. But of course there should be questions to be asked.