For sure...
...the worst case is probably not those browsers, but earlier versions that think they can but had all sorts of bugs.
I think Lynx will ignore the CSS, but you'd still probably be better off using Lists for the indentation - it'd just look like the original nesting that we had on IWE.
Of course, user selectable methods are the best alternative, as long as the software can handle it. Means you'll have to isolate the features as best as possible, and do some additional testing with the major releases. But since EZBoard never seemed to test things, you have a pretty low standard to live up to. :-)
