I'm at just shy of 60k miles on waste oils in my IDI and the fuel savings have paid for a new engine several times over. I haven't had to pull the head yet but have looked through the injector bore and haven't seen anything abnormal. This is ATF, motor oil, gear oil, transformer oil, hydraulic oil....basically anything petroleum based has gone through my truck.
I dispute your assertion about gumming up of the rings since I haven't seen increased oil usage, extra smoke, lost power, or any of the usual side effects of bad rings. Maybe someday I'll have reason to pull the heads and can get a definitive look at what, if anything, the WMO has done.
If the mix isn't burning right, you'll get extra smoke which is incomplete combustion. The pressure inside the cylinder blows everything unburned out the exhaust. I just don't see how the modifiers can resist the heat, not even smolder, and hang on inside the cylinder and not get blown out.