using that service, things should "just work". Hopefully this will be
primarily amusing, and people won't abuse it.
-[[!img http://cdn.libravatar.org/avatar/ef9dddd859f1f5a1fd6442a1ccf872ef?d=retro]]
+<img src="http://cdn.libravatar.org/avatar/ef9dddd859f1f5a1fd6442a1ccf872ef?d=retro">
More importantly, but much less fun, the double encoding problems
(where mails would get double-encoded if any of the headers contained