Try adding the following user CSS to your Display settings. It seemed to work for me, though it may not work for all browsers, and may have other effects too. Up the number of repetitions of ul to make the limit deeper.
I personally believe that this is the most sensible note read thus far in this thread: naively I would answer that it can't work because nodes are not implemented as ul's - but that is what I also naively assume. In fact I just checked with firebug (although a CTRL-U would have been enough) and it turns out that indentation is precisely handled that way. More precisely the elements are ul.indent's thus I would include the class in the css spec: all in all as a solution it is slightly clumsy, but indeed it does work!