A simple-ish way of subsidizing some of that effort is to just make a subreddit for arxiv submissions and link to the comments section from arxiv-sanity for a given paper. You still don't tie into other communities, but if someone has something to say about a particular paper it provides a straightforward mechanism (until the, what, 6 months at which point the submission is archived and can't be voted on or commented on any further). You only need a couple moderators and some strict rules (automoderator rule to only allow submissions from the arxiv-sanity user, etc).
