There have been many comment layering systems for arxiv, none of which seem to have taken off. Also, users are pretty split on whether they want this: http://ww

There have been many comment layering systems for arxiv, none of which seem to have taken off. Also, users are pretty split on whether they want this: http://www.nature.com/news/arxiv-preprint-server-plans-multimillion-dollar-overhaul-1.20181 http://www.nature.com/news/arxiv-preprint-server-plans-multi... . Personally I'm not in favour of such a system, as it's unlikely anyone would spend enough time to write a high quality comment that won't detract from a paper.