He and jesta are worried about Sybil attacks. Nothing stops a Sybil attack at the current 25% rate, right?
Lower rewards to established authors would mean that they have to post less, yes. And that's a good thing - would you rather have several people with several interests and everyone else working for free, or rather more authors and more diverse content, and more people receiving money for their work? It's all about a sightly better reward distribution and people actually reading the articles vs. mindless upvoting of established authors, because their articles pay out.
Also, being limited to posting less times a day, means that you will push for higher quality articles.