I just noticed that the Charting Plugin page utilizes several little icons like this:

Which are generated by this WML code:

Note that "(!)" represents *required*, "(-)" represents *not required* and "(+)" represents *conditional*

This is the first time I have seen these used...  Are these listed in the documentation somewhere?  Are there more of them?  I would expect to see something like this listed in the "Plain Text Markup Help" pop-up