Hallo Werner,

I know what you mean. Normally, when reading the advice that input voltage should not rised above Vcc+0.3V, this tells that there is PROBABLY some diode internally connected from input to Vcc. And normally it's ok just to have input current limited, when planning to work with higher input voltages.
Sometimes this assumed internally diode is some parasitic substrate junction, and normally damage can be prevented by limiting current with resistor, as you did it.
BUT: There is no rule, that you can depend on it!!! Sometimes there are other mechanisms running, which result in damage.
Assume that there is NO such diode, but a parasitic transistor, so you will bias it's basis-emitter- or gate-source-junction, when applying overvoltage. Then, limiting of input current is not enough to prevent that internal parasitic transistor is switched-on. Think also of a parasitic thyristor which can be fired-on...
Means, internally switched-on current can be much higher than your limited input current and can indeed result in total destruction.

I would even not trust a schottky-diode clamp in your situation. I would connect Vref to Vcc and use rail-to-rail opamps, also running with Vcc.

Bye,
Kai