The italics are properly formatted when I publish a chapter, but at some point my italics change to _underscored text_ and it's driving me up the wall. Any idea what's causing that, and how to make it stop?
You have an errant space at one end of your italics. For example, you're trying to do: I [really] want that cookie. But instead, you're doing: I [really ]want that cookie. For whatever reason, the interface can't figure out how to italicize that space, and so it rejects it and puts underscores (which might be part of the basic formatting system, but I don't use that). Anyway -- check your spaces, and you should fix things up.