With "honest voting economy" you mean that whales decide what gets seen and what doesn't?

Social media platforms can function well when votes are broadly reflective of each person's individual subjective appraisal of the content. This leads to a platform that sorts and rewards content in a way that represents the taste of the general users.

Unfortunately, as you pointed out, due to blockchain security reasons we can't have this. We instead have stake based voting and ideally we wish for stake based voting to approximate general consensus in terms of tastes as well as possible. By far the best way for this to be done is if stake weighted votes are cast honestly by the individual stakeholder to best reflect their subjective appraisal of the content in question.

It may be that the stake weighted honest subject appraisal of content deviates from the general honest consensus if all votes were equal, and to that extent it is undesirable. But that would be a problem of 'bad taste' on the part of our largest stakeholders as a whole.

However, if stakeholers are paid considerably higher to vote in a manner that's not consistent with their subjective appraisal of content, say for example, they're paid more to vote on a post by a vote buyer, then they're voting indifferently and pocketing the lion's share of their voting rewards. It is the exact same accusation mounted at self voters: voting in response to where the money is going (into one's own pocket) rather than one's honest subjective appraisal of the content.

In here I'm of course strongly implying that the problem of indifferent voting is far worse than the problem of bad taste. Using vote rewards as promotion completely undermines the system for this very reason. They're strictly incompatible with what we're trying to build. The EIP was designed to reinstate honest voting, yes with the imperfections of stake based, but not the failures of indifferent voting. That means that by definition it was designed to fight against the use of vote selling services I'm afraid.

Look at it this way, if there are insufficient downvotes going towards vote sold content, then over time more and more rational stakeholders will all choose to sell their votes instead of casting them honestly. Why choose 50% returns when you can get almost 100% returns right? That means that over time by definition content quality will drop as there is nothing left to voluntarily reward content based on honest subjective appraisal.

Likewise, if there are sufficient downvotes going towards vote sold content, then those selling votes will be making even less selling their votes than they would curating, so why would anyone sell their votes?

Do you now see the equivalence of self voting and vote selling? Do you now see why it's difficult economically speaking for some reasonable mutual co existence between vote selling and honest curation?

Maybe in theory the market will balance out to the point where vote sellers are getting just slightly more than honest curators, but no enough that there's a general shortage in the latter. But in practice I fear this would be too tenuous an equilibrium to reach.