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.
> The distinction between "has value for the submitter of the job ad" and "has value for the entire community" is an important one.
I disagree. For example if there is a typo in a URL could take a while for the poster to update it and they might not even be able to edit their submission if it's not identified in time. So if a community member says "link to xyz.com should by xyz.org" that would help other community members who wouldn't know what the correct URL was meant to be. That kind of comment has real value to everyone and not just the submitter.
> Comments that only meet the former test can just be sent directly to the submitter by email or whatever.
Lets be clear (because I've already stated this twice and it still seems to be overlooked) I'm not advocating that comments should be enabled. I agree with the point that those kind of comments are better off sent out-of-band because they don't offer enough value to justify the inevitable low value comments that would also follow. The only point I was making was that the distinction between useful and interesting shouldn't be overstated because they are typically (though obviously not always) linked.
I didn't. I couldn't even if I wanted to, as I always create a new account once downvotes are unlocked as I don't like the temptation of destroying discussions for topics I don't agree with.