Hi,
I have just committed a trivial change to Parser.php. We replace "~~~" with [[User:Username|Username]], and "~~~~" with that, followed by the date/time. Now, "~~~~~" inserts just the date/time, without the username.
I got the idea from http://en.wikipedia.org/w/wiki.phtml?title=Wikipedia:WikiMoney&diff=2852...
Greetings, Timwi