This bug breaks the edit conflict resolution process.
The upper field, which is supposed to show the stored version, shows the version by the current user (just as in the lower field).
Bug occurs with MediaWiki 1.16.0beta2 and latest SVN.
MediaWiki versions <=1.15.3 don't seem to be affected.
I'll take a look at this myself.
Version: unspecified
Severity: major