Theoretical comment spam like you described could be fought with automation pretty effectively imo. Once a farm is detected with the help of a relational database and some sophisticated analysis algorithm, the farm is done, and the cost to set up a large number of accounts puts a huge risk on starting an effort like that. Even with the relatively low account creation cost right now.
Imo shooting all small users because of that possible scenario is the wrong approach.
Also, the scenario you described doesn't need a threshold of an equivalent of currently ~3$
I made a small test. My 13k SP vote adds 6c to a 0$ post, but 24c to one with 30$. Raising the rewards for the big one in return lowers the rewards of the small ones. I will not like this ever. Going to linear was good.
Convergent linear should be very close to a 50-60% tax at the lowest end
From the graphs, it was like -40% value right at the start, and +20% at the peak
I don't know if detecting low level profitable farms is as you as you say. Keeping in mind many downvotes are in the hands of unsophisticated people. Put it this way, imagine Steem was $15 and there's ample incentive to try as hard as you possibly can in sophisticated ways to vote farm while avoiding detect. Making multiple seed accounts, then spamming RC to create more accounts from those seed accounts, then spreading them into clusters with only minor overlap, but moving funds and votes in a way that's dynamic, with comments being a combination of AI and generic messages in a foreign language etc.
Basically imagine you tried your hardest, or even someone considerably more technically sophisticated tried their hardest to evade detection under linear, and compare it to under convergent linear. I'd bet the former would be far more elusive.
Remember, n^2 was someone with 1000x your stake got a vote 1,000,000 your weight. Compared to that, this is nothing.
Also, I believe over time, as your curation project gathers more momentum, it'll easily break out of the starting part of the curve.
I mean, just look at the comments of minnows here and elsewhere. They hate the whole EIP because of this part.
They say we won't onboard the masses like that, and I fully agree. All efforts to fight abusers don't help when all the saved rewards go to the top instead.
There is no enthusiasm for it to be found on the base, the only ones defending it are the ones not affected.
Steem at 15$ would bring the threshold to 300$? I don't want to imagine that.
All data is public, who created which accounts and where funds move. It just has to be done, we have the minds here to set it up.
With this carpet bombing approach we disincentivize new people even more. They don't have the reach, which is perfectly normal, but then they get penalized for it. Even if my project and others get over the threshold (which would require several millions in delegations when we keep up the amount of curation we do right now - besides that I'm not viewing it as our problem mainly, but a problem for the platform as a whole), small users will never feel like their voice matters unless they follow the big ones.