When two people are editing a page, a notice should be displayed explaining that someone else is editing at the same time and that the edits will be merged. See Concurrent Editing and Merging Changes on Atlassian's Confluence.
The message there looks like:
This page is also being edited by [User's name]. Your changes will be merged with theirs when you save.
Identifying the user seems problematic from a privacy perspective, but the rest is good.