@Gabe: "What does a multi-letter keytip mean? Do I hold down Alt while pressing the first and then the second letter? Do I only hold down Alt for the first letter? Something else?"
In this context, they're used to display the characters that corresponded to the old menu shortcuts. E.g. in the picture above (aside: wow there's an actual picture in Raymond's post!), "FB" is bold because in the old UI, if you pressed Alt, then F for the Format menu, then B for Bold, you'd get bold. So you could chord it as Alt, F, B; as Alt-F, B, or probably as Alt-F (continue holding Alt) Alt-B. Though I'm not sure about the last and can't conveniently try.
[I *think* this didn't post the first time; sorry for the spam if it did.]