New users' first contributions to a site, by their nature, often require improvement. There are different methods of dealing with this, and I am looking for **evidence** that would help understand which are most effective, where "effective" means "this person becomes a positive contributor for the site". I am particularly interested in smaller sites; what works on SO probably doesn't apply to Hermeneutics and vice-versa.

Some people deliver constructive feedback through [polite, friendly comments](https://meta.stackexchange.com/a/140578/162102) asking the user to edit. Others make the edit themselves (and perhaps leave a comment explaining it). Some downvote and move on.

I have heard people make all of the following claims:

* constructive comments, no matter how well-written, make new users feel criticized
* new users are more offended by people editing their contributions than by comments, so we shouldn't do this until they understand the community aspects of content better
* new users are more offended by comments than people just fixing it for them
* new users don't mind downvotes (they probably don't even grok the voting system yet)
* going straight to a downvote is the worst message you can send to a new user because you didn't even try to help him first

Obviously not all new users are alike, but which of these positions are best supported by what we've seen happen in the past? What is the best way to guide new users whose posts need some work?

**Update:** [Rachel's answer](https://meta.stackexchange.com/a/167474/162102) is some of the finest writing I've seen on Stack Exchange on the care and feeding of new users. Her answer should find a life beyond this question somewhere. Without wanting to slight her, I am accepting [Shog9's answer](https://meta.stackexchange.com/a/167510/162102) because it addresses the past trends I asked about here (so it is the one that most helped me).