It's change of economic model that, simplifying it to something like "this post will get x instead of y" basing on a shift in rewards is wrong, because it doesn't assume shift in behavior (which should change because of shift of incentives).

True. However for most users the chances of a large account coming along and upvoting their post will remain small, even if the shift in incentives does change behaviour. As such it's useful to understand how their post payout would change, as a "pre-behavioural" starting point.

Currently, user without SP could take advantage of bit bots, go to trending, gain reputation all that while having negative cost (i.e. earning on that), because selling SP to bit bots is just the easiest way to earn. With 50/50 it will no longer be that simple, because you could earn with your own SP by voting for good content as much as self voting or selling SP to bit bots.

I think that downvotes will be the change that stops the majority of the bid-bot issues. This is worth the experiment.

Large accounts currently earn around 21% of vote value in curation under 25/75, so this will probable double to around 42% of vote value under 50/50. It's still a long way off the close-to-100% of vote value that could be earned by circular voting or higher rewards from vote selling etc. It's a step in the right direction but it will be interesting to see how it actually changes behaviour. Economically, the incentives still don't align towards manual voting.

The CLRC seems to add little value, but again hammers small earning accounts / new accounts as well as comment engagement. The combination impact of the HF21 changes on such small earners is very large. This could be mitigated to some extent by removing the CLRC change from HF21.