I'm not sure what you mean by incident on that user across all posts, but if I understand correctly then the abusers can create many new accounts and have each one only post once (per period). There won't be anything to combine across posts with only one post per account. This is even worse than just spamming because all those new accounts impose overhead too.

There are other implementation issues with this such as the computaitonal overhead of aggregating, the fact that the posts aren't paid at the same time, etc. But those aren't worth getting into because any attempt to impose sublinearity when there is no mechanism to force users to keep their stake in a nice bundle where it can be counted (and therefore penalized) is pointless. And even if it were, It is also very questionable from the perspective of STEEM value whether it makes sense to introduce a strong incentive for anyone who already holds STEEM to sell it and reduce the incentive for anyone who already has some STEEM to buy more. That sounds like a recipe for disaster to me. The whole premise is looking at things too myopically from the point of view of voting 'fairness' (questionable to me as "one SP, one vote" is also 'fair' in a lot of ways) and losing sight of the fact that everything rests on top of investors attaching a high value to STEEM. If that isn't the case then voting means nothing because you will be voting on nothing but crumbs.