I've just done a few quick tests in our qa/2.x development environment and was unable to reproduce this issue. Normally, the username on the description modification history is a hyperlink to the user's profile mod history - I noticed in your first screenshot that this is not the case. Is it possible that the atomtest2 user was deleted, and then a new one created at a later date?
Can you see your own modification history on your admin account, or is this happening for all accounts?
Have you tried restarting MySQL, turning the setting off and on again, or any other maintenance tasks to see if it helps? Is there any chance that local code customizations might be interfering with this - for example, a custom theme not including the right template elements or affecting the page JS?
Anything else you can share that might help us narrow down the issue is welcome.