if you have 50 people on a forum and all of them rep each other as much as they can, but they all post different amounts.. you can rep 10 people a day, and you need to rep 30 people to rep the same person consecutively, so.. seeing as 10 reps a day, 30 to rep the same person - that means you can only rep the same person once every 3 days at least.. therefore there will/can never be a shortage of posts to rep that person for UNLESS they post less than once every three days
since practically everyone on mx with significant rep is above 0.333(...) ppd, the issue of how many posts someone has never comes up, because you will never get to a point where you can rep ANYONE faster than they can post, so everyone has the same opportunity to be repped regardless of how much more they are posting than the 1 post every three days lower limit
thats even ignoring the actual reasons that people would rep someone.. which has nothing to do with how much they post.. you dont see someone posting and rep them just because you saw them posting.. people rep others for content of posts, or whether they like that person, or how much rep they will get in return and etc etc etc, nobody is repping based on how much they see someone posting, or as an impulse JUST BECAUSE they saw someone posting so they have to rep them for some reason