One argument for conservatism: if physicists want a commenting system, why hasn't SciRate taken off?: <a href="https://scirate.com/" rel="nofollow">https://scirate.com/</a> The interface is clean, it has a lot of nice features, etc. It's gotten some traction in quantum info (my field), but the comments are rarely used. You can chalk this up to network effects (chicken-and-egg), which direct arXiv hosting could solve, but that problem can probably be eliminated by taking the minimal step of allowing the authors to link to the SciRate page from the arXiv page.<p>No, I think the major feature about having the arXiv host comments directly is that it would <i>force</i> physicists to engage with folks who comment on their paper, because otherwise there would be unanswered criticism attached ("stapled") directly to their public-facing papers. Maybe that's what we want, but that's a huge step and there are a lot of ways for it to go badly.<p>Here is a mockup that Paul Gisparg made for author-curated links on arXiv article pages. See the "Author suggestions" column on the right: <a href="http://www.cs.cornell.edu/~ginsparg/arxiv/1212.3061-mockup.html" rel="nofollow">http://www.cs.cornell.edu/~ginsparg/arxiv/1212.3061-mockup.h...</a> Allowing links to places like SciRate plausible solves most of the chicken-or-egg problem by allowing the author to designate "the" place for public discussion without picking a particular site to win or lose, or bundling <i>release</i> of a paper with forced public <i>discussion</i>.<p>Shameless plug: folks here may be interested in my blog post about the future of academic papers and how the arXiv influences that: <a href="http://blog.jessriedel.com/2015/04/16/beyond-papers-gitwikxiv/" rel="nofollow">http://blog.jessriedel.com/2015/04/16/beyond-papers-gitwikxi...</a> There was good discussion on HN last year when it was posted: <a href="https://news.ycombinator.com/item?id=9415985" rel="nofollow">https://news.ycombinator.com/item?id=9415985</a>