Wikimedia Bugzilla is closed!

Steps to reproduce are below. Unexpected behaviour occurs in step 5:

Step 1: Create a message at [[MediaWiki:foo]] that says "this is a test".
Step 2: To the end of /index.php, add: print '<h2>' . wfMsg( 'bar' ) . "</h2>\n";
Step 3: View a page on the wiki. The footer of the page now contains "<bar>", as expected.
Step 4: Move [[MediaWiki:foo]] to [[MediaWiki:bar]], and then view another page on the wiki.
Step 5: What happens: The footer of the page still contains "<bar>". Would now expect the footer of the page to contain "this is a test".
Step 6: Edit [[MediaWiki:bar]], no need to make any changes, and then save (i.e. make a null edit).
Step 7: What happens: The footer of the page contains "this is a test", as expected.

Conclusion: There is caching of MediaWiki namespace messages occurring, but that caching does not get invalidated or refreshed on page moves, even when those page moves directly affect messages that are displayed to the user.