I don't understand the utility of this. Maybe it works for things like noise ordinances, but I can't imagine finding common ground with people who want me dead or imprisoned simply for existing.
Every Body Corporate Strata in Australia basically goes through something like this at least once a year (by law.) Questions are posed about what to vote on and you either vote for, against, or abstain.
Something like Polis would be good for putting forward ideas throughout the year leading up to the vote, as it would find a consensus of ideas and help shape what you eventually vote on (you decide as a body corporate.)
Some Strata are hundreds of people in size.
Those people came to those views somehow. I'd hope that a less radicalizing social media platform might move them away from those views. Finding common ground isn't just about figuring out where people currently agree, it's also an act of persuasion convincing people to change views to then-mutually shared views.
Wanting people dead or imprisoned simply for existing is the sort of inconsistent view that is likely easiest to change by moving people out of radicalized spaces...