With a somewhat valuable but straightforward comment, an upvote with no further discussion is optimal, because both the author and the readers understand why it’s good.
With a worthless but ingenuously written comment, the readers gain nothing from further discussion, but commentary helps the author to more easily discover his error. Do what your decision theory requires regarding the good of the many vs. the good of the few.
With a somewhat valuable but straightforward comment, an upvote with no further discussion is optimal, because both the author and the readers understand why it’s good.
With a worthless but ingenuously written comment, the readers gain nothing from further discussion, but commentary helps the author to more easily discover his error. Do what your decision theory requires regarding the good of the many vs. the good of the few.