I wonder if there might not be some currency buy-in model that would work. Instead of your in-site "cred" getting bumped, maybe that cred is worth something tangible. Maybe in order to buy into the site you have deposit $5 worth of cryptocurrency X and to ask a question you have to "pay" a dollar worth of that currency and those dollars are "credited" based on how the answer/upvote pool decides.

I can think of at least 10 problems with this approach, but I think it might be feasible.