Returning to the pool just means that all payouts will be proportionately larger as a result (the increase will be slightly more to curators overall). All of the money in the pool gets paid out to someone.
This is a vast oversimplification. What actually happens for everything that is "returned to the pool" is that it inflates the value of everyone's vote proportionally to their stake. (Each rshare becomes worth more of the rewards pool.)
Whenever that happens, it broadens the equity gap, makes whales and bidbots more powerful relative to everyone else, and exacerbates most of the perceived problems on Steem. That's where most of the self-voting and circle-jerk and bidbot profit comes from, and it's at least part of why Trending is constantly full of crap.
"Returned to the pool" in the guise of @steemit's declined stake and other smaller factors is already a pretty big problem and HF20 is just going to make it larger.
'Inflating the value of everyone's vote' makes no sense when the value (reward pool STEEM per rshare) is variable not fixed (as a function of the amount of voting and somewhat the schedule of actual payouts), and it can't increase any 'equity gap' because the value is the same for everyone.
The pool will reach a new equilibrium with slightly more going to curators and slightly less going to authors (specifically the authors who receive early votes, whether self-votes or not). In practice the shift will not be much at all; the vast majority of the pool will still go to authors. In many cases an author who gets a little less by losing out from the early votes will then get a little more from the pool being bigger, for hardly any net change. It is very unlikely that most users (unless they routinely use the instant self-vote) will even notice a difference.
I'd like to see a more substantial change but I can't get worked up about this either way because it is almost nothing. I consider it in the category of small code tweaks.
This is absolutely not true. The value is greater the greater your stake. The increase in value of votes from anything that "returns to the pool" increases the value of your vote 40 times as much as it increases mine, because it inflates the value of every rshare equally and you distribute a lot more of them than I do.
Example: my 100% vote is 8c, yours is $3.38, and @smartsteem's is $177.26. The base "return to the pool" from HF20, absent any change in behavior, will be about 7%. (We'll actually get a lot of behavior changes and it will be less, but I'll use this number for convenience.)
A 7% increase in all of our power means my vote will now be eight and a half cents, yours will be $3.61, and Smartsteem's will be $189.67. Thus a much larger equity gap, and whales distributing a much larger portion of the pool relative to everyone else.
No, that won't happen. Think of it this way: If 1000 STEEM goes into the pool each day, 1000 STEEM comes out of the pool each day. Nothing about this change affects how much goes in, therefore it also doesn't change how much comes out. Assuming the same number of votes by the same amount of SP, each vote is allocating exactly the same portion as before (though it is allocating it a bit differently between authors and curators).
More will go to curation rewards and less to author rewards, but amount allocated by each voter will remain the same.
Even if what you wrote about the increase all of our power were correct, the portion (i.e. fraction) distributed by whales wouldn't be any different than before. Your own example demonstrates this. In the first case, @smartsteem is distributing 98.09% (177.26/(177.26+3.38+0.08)) and in the second case @smartsteem is distributing 98.09% (189.67/(189.67+3.61+0.085)).
The only way your claim about a shift of "gap" could be correct would be whales and non-whales systematically differ in how much extra they award to authors by the current (to be removed) early voting bonus to authors. That's possible but certainly not obvious, and your example didn't demonstrate it (or even claim it).
Your assumption is incorrect. What you want is "assuming the same number of rshares used to assign the pool" and HF20 will change that number by destroying some of them in the post payout process.
The fact that some of the rshares are destroyed after the vote doesn't really matter, they're still not being used to determine the rewards. So it's equivalent to a dramatic reduction in voting.
It's probably easier to think about this in some of the other ways "return to the pool" happens, like @steemit not voting. But it's the same effect.
Again, 1000 STEEM goes into the pool each day, which means 1000 STEEM goes out. If 1 million SP place votes, then STEEM is awarded out of the pool at a rate of 0.001 STEEM/SP. What happens in between doesn't matter.
There's no way around this.
(Obviously these numbers are made up and hypothetical. Substitute the actual numbers and the actual rate of STEEM/SP will still remain the same before and after.)
While the numbers end up the same, the calculations have different denominators, and that turns out to be pretty important.
The total Steem in the pool is determined based on the total number of Steem in existence, while the distribution of the pool is determined based on the SP used to generate rshares.
Now that SBD is closer to normal that ratio is the primary factor determining things like the self-voting APR and the total profit available in a vote-selling transaction. It's a big deal.
I'm only going to say this one more time. The reward generated per SP will be exactly the same as before The number of rshares used to calculate payout will be lower, but the reward per rshare will be higher. The two differences will exactly cancel out.
By design, authors will receive (slightly) less of that reward and curators will receive (slightly) more. Neither you nor anyone else has yet come up with a coherent explanation why this is a bad thing.