Can you link to some other site's Meta that outlines their policies on the subject?
Personally, I used to delete this sort of answer, figuring that it was part of the reason deletion was there; to clean up junk posts. The more I discussed the subject with other moderators, and read and reread the documentation here and on (formerly-Meta-Stack-Overflow) Meta Stack Exchange, I've changed to the opposite. I don't delete anything that's a non-joke attempt at answering the question, even if that answer is buried in a little cruft. If a post is entirely tangential commentary, a comment/reply to another answer, or trolling/offensive/spam, then I delete. But if the post makes some attempt to answer the question, I don't delete it. Ward's answer over here outlines some of the discussions on MSE on the subject.
Note, that I usually downvote low quality answers. I expect expert users to post comments outlining how an answer is incorrect, low quality, etc. When I have time/capability, I leave comments as well.
Lately, if I received a flag on a post that deserved a downvote, I would downvote and mark the flag as helpful. But I can see how confusing that is, since anyone can downvote, and that's not properly 'moderator action'. So I no longer do this. If a 'very low quality' or 'not an answer' flag doesn't point to a post that should be deleted, I decline the flag. This is what happened to your posts.