playBunny:

Pedro, Rex Nihilo: So someone gets a huge rating with their first few games. That's great. I'd target them as ripe for plucking. [] A few games with them and I've either found a new opponent to play or I've earned a nice handful of points for myself and sent them on the way down to their natural level. If it's cheating it's certainly a most unsuccessful form. High rated players should welcome such people with open arms, lol. []

It's very successful form, as you can see on these examples:
Molatov and his Backgammon rating

TOPGUN and his Extinction Chess and Loop Chess ratings


I don't want to have more people like this on BK. And if you allowed reseting BKRs, I'm sure there would be many of them.

Pedro: The other three opponent's rating don't matter? My understanding is that it's the average of those four games, so I rather think they'd matter as much as the first.

The other three games will affect your rating, of course, but are not relevant for the fact whether you will get such an extremely high BKR. That's only the first game. If you have no BKR and play four games with the same opponent with a BKR of, say, 2300, and you win the first game and lose the following three, your prov. rating would be 2500+. But if you lose the first and win the other three games, your BKR will not be that high. I bet it would even be under 2000.