This is actually a bug report for diffs with tab indentation changes, see http://code.google.com/p/reviewboard/issues/detail?id=1780

This seems to be the best way to show the problem. If you download the diff you can see a clear tab indentation change .... yes this is python and using tabs is stupid, this is just a bug report :-)

If you view the diff - there is nothing to see!

In RB 1.0.5.1 (with a larger diff, where there a non indentation diffs) you can expand the diff and see the indention changed BUT there is is no highlighting.