We all need to proofread ourselves more. But one of the problems is that we don't see what we wrote, but rather what we were thinking when we wrote it, so most of our typos are invisible to us. I'm also a programmer and we can have an error in our own program that we cannot see, but as soon as someone else looks at it the error jumps right out at them. It's the same with proofreading ourselves. The only technique I have found to be at all effective is to read what we wrote out loud, word for word, even if it's still only inside our head.
As for the question of moderator editing, I'm generally against it. However, if it does prove to be necessary, then I would insist that the original text remain intact and that the editing be presented as a note suggesting a correction. IOW, the "service" could still be rendered, while at the same time honoring the original.