Anything which introduces the possibility of cash payments to members - especially automatic ones - makes me start wondering about how it might be exploited or abused. A possible way to soften that is, in the case where people subscribe to be a member in the first place, a person could accumulate credits as a discount against their next payment. So no cash rebate, just a discount.
For the record, as I hinted earlier, this seems to me like an extreme version of gamification, and seems to me to be bad a idea, certainly for the sorts of community I’d want to be part of. But also as noted above, I don’t think it’s fruitful to debate whether or not this is a good idea, as if there’s a right answer, because there isn’t - it’s a matter of opinion. Someone who might eventually set up such a compensated micropayment community will discover how well it works, and anything else is speculation.