4 apps (kbforums, forums, questions, and wiki) had issues sending notifications for objects with non-ASCII characters in their titles. We didn't (and still don't) have tests to catch it and we got bug 634608. We should improve the test coverage of consumers of the new notifications app, since a lot of their functionality is not covered by notifications tests themselves. Including, but not limited to, adding tests to ensure that every event can handle Unicode.
Or perhaps we can make the notifications app either overcome the unicode issues (probably not) or else test all existing Event subclasses (metaclass registration or something). Adding more framework to handle common email-building cases (which we did plan to do) is another option. I hate to add a big test burden every time we create a new event.
This issue was that we were formatting unicode into byte strings to create e-mail subjects. If you can think of a way to centralize that, then win. If not, we need to test anywhere we format strings like that.