Copy and paste
I'd say that "This is called a merge. Nobody is trying to delete material or steal credit. The point is to organize the material better." is a pretty sweeping statement: in actuality any of a number of things may have happened (including deletion of material, or stealing of credit). This just sweeps it under the rug.
A merge can only be done by an admin, and if it can be reversed, it can be only be reversed by an admin. And, sure, something sold as "merging" can be vandalism. There is no telling if that is the case without examining it on a case-by-case basis. - Brya 05:33, 22 May 2011 (UTC)
I apologize if it's sweeping. But the number of times someone abuses a merge is so rare, and so easy to reverse that it's close to the truth. A merge can be done by an IP. I could go onto any Wikipedia in the world and redirect an article, and copy its contents into the redirect target. Which means it can be undone just as easily. The only times when you'd have a hard time undoing it is when it's actually been a firm decision by a consensus of editors to merge something, in which case it's a good decision, and not some kind of insult.