Bad feedbacks are parts of the process, period, and I think that reiceving bad feedbacks is also an important point because it gives you another point of view that you might not have think about, which is maybe not well formulated, but is still a real thing.
Sometimes people don't have the time to make great feedback, or sometime they are just not experienced enough to make them, or the map is so terrible that it doesn't need more explanation, it's just terrible that's it. But the issue they reveal might be an important point that everyone missed, especially about these great feedbacks, which most of the time are only a continuation of the mapper's own perspective, "put a path there", "move this here", "bla bla bla", but they rarely bring another dimension to the mapper's perspective.
Who are you to judge if the feedback is good or not, you can't only judge a feedback by it's presentation, someone could make a huge feedback with a lot of pictures, explanations and stuff, while not pointing out any important issues in the map, while someone could say, "The map sucks it's fucking overscaled in the mid" that it could nail the main problem of the map in one sentence.
The point is, even if the complains are too vague/rude/salty, you need these bad feedbacks, and it's usefull for the mapper to question himself about his work and if he is doing it the way it should be.
There are moderators here, and imo it's enough to get rid of the insults, even though I never seen one in a map topic tbh.