Others (and not only moderators!) editing someone's post is an integral part of Stack Exchange. For background, I recommend you read the entirety of these three pages:
The second of those three says (a bit bluntly):
If you are not comfortable with the idea of your contributions being collaboratively edited by other trusted users, this may not be the site for you.
Nonetheless, as you see on those pages, there are limitations on what edits should be made. Specifically, edits should improve a post — obviously a subjective criterion — and should not change its meaning — also a little subjective. If you see an edit has been made that changes the meaning of a post, feel free to call attention to it here on Meta or in our chat room. If the post was your own, feel free to re-edit to your satisfaction.
Adding meta-info to a post — that is, adding info about how or in what order or by whom the post was written — does not improve the post. For clarity's sake, the post should be organized so it's readable, not so it marks who wrote what part of it. If someone wants that, he can look at its revision history. (Click on the last-edited time beneath the post to see its history.)
One more point related to the topic of "the user may not agree with what is being said in his name": Rarely, the following occurs. Someone makes a non-substantive edit, by which I here mean an edit that doesn't change the meaning of the post as a whole. The edit is one that the community approves of — either the community explicitly agrees to it on Meta (or in chat) or, failing that, it's a moderator's assessment of what the community would agree to — so it won't be reverted. But the post's author cannot abide by it. For example, perhaps the post is by a Foobarist who insists on referring to his god Foobar as only "The One and Holy God" and the community insists on editing that phrase out. Then the post author can, if he wishes, dissociate himself from the post.