The glazing is pretty hard (glass) but of course it can scratch over time...
Maybe a change of diet? :)
Most quality WC's have fully glazed trapways, but if a plunger or hydraulic ram cannot release a clog, might it be deeper down than the siphon?
I suppose if you had to punt, some vinyl or surgical rubber tubing might give some protection in a pinch but I always think it is the metal corrugations (against metal pipe mind you) that makes a snake effective.
Thanks for the thoughts. Will take a look at the General. Looks similar to the Ridgid.
Brad, the immediate problem is anthropogenic in origin, but not digestive in nature, so recommending a dietary change won't help. 'nuff said.