Jon: OK, so I checked, and indeed function arguments in Python are Italicized. Sorry for not noticing this—it was a bit subtle at a small font size, and I really was looking for italicized comments, like I saw in a screenshot someone posted.
Also, in LaTeX, function arguments are again italicized, which is nice. However, I was hoping that e,g, \emph{…} and \textbf{…} would also be shown in Italics and bold respectively, as in Textmate. That doesn’t seem to be happening. I guess one would have to tweak the LaTeX grammar file…