Atom + CSS
I tried some minimal css on an experimental Atom feed and the results started to look promising - on Mozilla. View source to see how it was done.
I then brought up the same page under IE, and it looks like IE didn't support a number of CSS features. Worse, it seems to be stripping and/or interpreting escaped markup. Finally, view source is not available.
Poking around to see if there were any workarounds, I came across this article by Tim Bray from 3.5 years ago...
Sigh.