Currently, if two people edit a wiki page at the same time, the second person to hit Save gets an error message.

It would be good if the second person could see a ‘user xyz starting editing this page X minutes ago’ message, so the second person knows to stay out. Some script in the edit page could ping the server every N seconds so that the server can tell if the first person closes the edit page withing saving.

You’d probably also need a way for the second user to force their edit if they want to, in case another user has accidentally left the edit page open for a long time.

Alternatively, you could notify the second person when they hit Save that the page was edited by someone else, and then offer to merge the second person’s changes with the first person’s changes.