Unless they changed it recently, if I reply to someone via the reply button, the comment just goes on my own wall not theirs. Then again I havent used the reply button in a long time so I guess I could be wrong about that. And if the newsfeed does actually work that way the yeah spamming would work to get yourself of his newsfeed faster. When the other guy spammed my wall it showed me two of his comments then bunched all the other comments into one entry on the newsfeed. This is why I think there is a time limit on the posts because from my experience, the guy spammed me repeatedly, I'm talking upwards of 300 posts on my wall and the revenge tab was still available on my feed for four days. Just my observations.