Most all 4-strokes on the market can be run on regular pump gas.
Fuel injected quads are less sensitive to the effects of ethanol than carbed quads, though it really just depends on the FI unit's programming.
I wouldn't worry about it unless you're seeing high engine temps and reduced performance.

Our zillas are different because they're quite sensitive to jetting and detonation.
A small change in jetting has a big effect on a 2-stroke, and the squish band on the 500's isn't optimal.
Suzuki had a problem with detonation from the beginning, that's where some of the differences between the 87 and 88+ 500's came from...they were trying to limit or eliminate damage caused by detonation (extra head stud, retarded timing in the CDI, etc.)