[_delirium]

On the latter point, I think you also need to cultivate some sort of trust relationship. People need to care about your feedback, and truly believe that your view might be better than the view they were holding. Just giving blunt feedback is an easy skill that everyone on Reddit has, so I think people are pretty used to tuning it out, especially if you give them any reason to attribute it to you just being grumpy/biased/jerkish.

One part of this, imo, is that the feedback-giver has to accept that they might also be wrong, and be open to admitting that their feedback was misguided or a matter of opinion if it turns out to be. That helps people to believe that it's not just the feedback-giver trying to impose their personal opinions, but actually well-considered advice.