I've always wanted arXiv to fill that role. I understand though that simple anonymous comments don't cut it. It can devolve into youtube comments quickly -- pe

I've always wanted arXiv to fill that role. I understand though that simple anonymous comments don't cut it. It can devolve into youtube comments quickly -- personal attacks to the authors, low effort comments, spamming, "trolling", etc. Those sites need a private reputation system: you can vote comments but the commentator is anonymous; it's hidden reputation should help sorting the comments.