When I moved my page from one space to another all of my username links to user profiles got prefixed with the old spaces key - and hte key then showed up in my pages content when being viewed.

ie:

dmackie
became
[PRJ:dmackie]

and the PRJ is now shown on my page.

The move page function should be smart enough to not prefix these kinds of links with a space key because they are not space specific.