I think it's a little redundant making a distinction between "useful" and "interesting" because either way the comment has value. However I do agree with the points you made in your other comment (https://news.ycombinator.com/item?id=22767319) and that the examples given of useful/interesting comments by the GP doesn't offer a high enough value to justify the inevitable negative and other low value comments. Which I think is the real crux of the matter. Much like why political discussions are generally banned on here, the signal to noise ratio just isn't worth the few valuable comments a submission might receive.