When I attempt to add a "user" journal entry note, I type it in, hit "Done", and when I try to read it later, it's empty. I can't even click the "Revert" or "Delete" buttons as they're grayed out. Am I misunderstanding the interface or is this some sort of bug?

In the classic BG2, I managed to add a note in that order.

1. Open Journal
2. Click User
3. click ADD
4. Type something
5. click DONE

Then you should be able to see your post with a date.

To delete that entery simply click on the message(not the date but message itself) and then click delete. replying..

This is what I'm doing. The game recognizes that a note was added and timestamped entry appears in the journal, but there's no text in the entry. I figured maybe it was some sort of font issue, but "Revert" and "Delete" being inactive seems like something else is wrong and nothing is being recorded properly.

Would like to bump this once. Not having ingame notes is an unfortunate inconvenience but I suppose if nobody can solve this I can switch to old school pen and paper..

First, you need to state which version of the game you are referring to... ALWAYS. Next, if you are using classic BG, the user journal has a structure that's not immediately apparent. If you make an entry for chapter 1 while playing in another chapter, then try to find it in the chapter 1 page, you won't. It goes into the page of the chapter that you are actually playing in. This means you cannot organise your journal retroactively, it must be done as you go.