So, it's a novel fight you're after eh!? (Just kidding, this will probably be much shorter. Edit: Narrator: It wasn't)
These are all very good points, and for the record it's with our discussion in mind I cast my vote for nay with some reservations.
At the end of the day, what I'm after is some proof of investment in the community for voting rights. I agree that a paywall alone for enfranchisement is, at best, insufficient, and at worst can create a scenario like you describe here. Perhaps I very much am underestimating the capabilities of power trolls (particularly as things grow in scope).
Donation in tandem with other markers, though, can signal enhanced commitment to the instance. I'm going to be donating (@TheDude - even more if you can make a 'sh.it.head' t-shirt via CafePress or something happen!), though all that really says is I want to toss the instance admins a couple of bucks, admittedly nothing about my intentions or character. But doing that, and buying the tshirt, and posting often, and having conversations like the one we're having now, I hope would signal that I am indeed commited to this little experiment.
Re: dismal conversion rates for digital products/services with a 'free' option - you're not wrong. But there's another angle to this which I'll mention not because it's directly relevant to this discussion here but a broader consideration: if we're really going to embrace decentralized, user-focused and enthusiast-supported platforms, at a certain level people are going to need to move away from this "I want it to be free as in beer" mentality. This will be, to understate it, difficult. Internet users have been inculcated to expect free-as-in-beer services in exchange for their personal information being bartered for so long that it's now the standard MO of most popular services. But that's not what is happening here. Electricity and costs for server upkeep exist, and while sh.itjust.works seems well positioned from a resource perspective it's all currently based on these not being a burden to TheDude. At some stage, if you want nice stuff to still be there, you gotta chip in. If you can't, you can still participate, but someone's gotta foot the bill, and we can't rely on that being TheDude (or any admin) forever.
Giving some perks to encourage donation, including it being a factor re: rights to enfranchisement, could help keep the corporate shitheads away. "Naw, we the users are keeping it afloat, we don't need your enshitification payout". Edit: But, in keeping with my 'Nay' vote, let's try some other stuff first re: ability to vote, particularly while overhead isn't a pressing concern.