One issue with doing flat rewards, even for a time, instead of the curve is that it opens up a new form of auto-voting. For example, if the rewards are proportional to stake for the first hour, then large stackholders can have bots watch which posts are getting first hour votes and pile in. The curves encourage voting before others, but not voting too early. Perhaps the early-voting-penalty time could be extended, and front-ends could build ways to delay manual votes for their users.