The first thing I want to say is that I am no longer inline editing posts. I wanted a way to respond to people's questions directly, and there is currently no built-in way to do this (though Jeff mentioned that "annotations" are coming soon).

In a way I was following [Jeff's example][1]. But I think now there is consensus that this isn't a good practice, so thanks, Keith, for setting me straight.

Now to jump in with my thoughts, edit to:

* Fix grammar / fix spelling / improve formatting.
* Make the post clearer or more effective.
* Linking to other resources related to the post.
* Add a warning if the post is dangerous (i.e. recommends solution with a security vulnerability)
* Add new relevant information missing from the post.

But do not:

* Change the meaning of the post.
* Add inline conversation.

I want to point out that Jeff has [explicitly told us][2] that Stack Overflow is going to be wiki-like and is not a discussion forum. Those with edit ability who have something important to add shouldn't feel bad about doing so—it's the whole point of the site.

  [1]: http://beta.stackoverflow.com/questions/6532/is-editing-other-peoples-posts-wrong
  [2]: http://beta.stackoverflow.com/faq