Rental agency said a $2000 comprehensive deductible on State Farm car policy was unheard of. Or was she promoting the rental agency in house insurance or should the deductible be lower?

A $2K deductible is not unheard of, but it is unusual. All it means is that the policy holder is self insuring themselves for small damage.

A suspect she was promoting the in house insurance, but the point is, if there is any damage, even minor dings, the State Farm policy won't cover it.

I will agree, a 2K is very high, most have 500 and about 1000 max. So with that, if you are renting a car, and showing your car insurance to cover it, The car rental company may have policy limits