Another idea might be to show diffs in the comment lines.
Some of us use navpops and you can preview a diff in a popup, but including a diff within a comment would of course make it so anybody could spot plain vandalism from whatever RC they are using.
I dont know how diffs could actually be made more concise in order to best fit, but it seems that we can at least indicate whether text has been added or removed and what text that is.
-Stevertigo