My personal policy on SO: (Almost) never downvote a question immediately; always explain first why something is missing or inappropriate - and also warn that downvotes are likely if it is not addressed because criticism on the site is harsh.

If that doesn't help, then either I can answer + edit at the same time, or I might downvote.

That's how I treat others - and that's how I hope to be treated, although usually that's not the case :-(