No, but it would be nice if we had a place where we could discuss scientific papers anonymously. Of course, to keep things concentrated, it would be nice if there was exactly one such place.
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.
Have you looked at PubPeer? There have been some very interesting posts there.