I played with this idea a bit over the weekend and came up with a notes tab on the persona window (zipped attachment below). There are three note tabs for each character, and a "shared" tab accessible by all of your characters. As far as I know, the only way to get the functionality you are looking for is to use the POI system that Drumstixx uses for his settings, but there is an issue that you have to watch out for when switching between characters:
For example, log in with Character A and create/edit some notes, then switch to Character B and create/edit some notes. So far, everything works fine. But if you
switch back to A again, you won't see any of the recent changes you made to Character A's notes. The changes will be saved, but you will only see A's notes as they were when you first logged in. You will need to log all the way out and back in, or do a /loadui to get the recent changes to appear on A. There is no way to actively refresh the POIs when you switch back and forth between characters.
This behavior is a bit squirrely and hard to support unless the user is aware of the limitations. In another thread it was suggested that an in-game book would work as a notepad of sorts -- I like that idea a lot better because the information goes back to the server when you save it.
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