On one hand we have discouraged writing "answers" in comments, and on the other hand, recently some answers were converted to comments (which "♦ moderators" are able to do).
We do want to encourage people to write answers, and we do want our (# of answers) / (# of questions) ratio to go up, but at the same time we do want answers (which allow users to gain rep and badges) to have some minimum standards. What do we want those minimum standards to be?
I'm sure there's Meta posts all over the network that say that just linking to a paper ought to be a comment rather than an answer, and that one needs to actually explain the relevant contents of the paper in a self-contained answer rather than just posting a link to a paper and making people read through the paper until they (may or may not) find a part that's relevant to the question.