I don't think that it requires creating another competing chain, just changing how rewards are gained and distributed. For example, you could create a scaling factor so that SP earned from posts and comments is 10x more valuable than SP that you purchase. While it certainly wouldn't eliminate the problem completely, it would decrease the power of those who have used their personal wealth to buy influence instead of earning it by participating in the community. Other factors could be your reputation, how frequently/consistently you create new content or comment on others' content, etc.

I don't like the fact that I see 1-day-old accounts on here with zero posts and 2,500 SP, which were obviously created to game the system and essentially price minnows out of the market. I don't think a 1-day-old account with no posts and 2,500 SP should have the same voting power as a 1-year-old account with daily posts and 2,500 SP.