This site has been posted here 6 months ago: https://news.ycombinator.com/item?id=16273171
It was a reddit-style exclusively for papers. Is there any info on what happened to it? Or do you know about any alternatives which have a similar concept (besides super-niche subreddits)?
I suggest Reddit. There's a lot of this kind of discussion happening there. There are big subreddits like /r/science.
FWIW, we (Crossref) found only 13 links to DOI-registered content in its lifetime: http://api.eventdata.crossref.org/v1/events?subj-id.domain=u...