> Yes, but that won't save you from getting -0.3V at the PIC pin..
> may this cause problems? For MCLR it is definitely out of specs

But is it ? The spec for MCLR isn't very clear. "Voltage spikes
below Vss at the MCLR pin, inducing currents greater than 80mA,
may cause latch-up"

And Section 9.9 of DS40300C (16F628 comparators) appears
to be in disagreement with the Absolute Maximum Ratings guide
(which doesn't actually say categorically that damage WILL occur)

AMR says, wrt to Vss, input range is -0.3V to Vdd+0.3V. Section
9.9 says Vss-0.6V. If the internal diodes are normal PN types, and
I assume they are, then the Vss-0.6V limit would be the one not to
exceed. Although the section implies that this is for analogue inputs,
the pin block diagrams shows diodes are clearly at the pin, not the
analogue module

In my case, I am specifically using the comparator spec because
in one instance that's where I had trouble with motor spikes. There
are now a few dozen units out in the field using Schottkys. Because
of the nature of the application, a safety test is performed on each
board before installation. Even the meanest noise can't make any
comparator pin go below Vss-0.1V

If you recall, my initial problem was voltages and currents very
similar to yours. I'm not saying that what you propose wouldn't
work, but research at the time led me to Schottkys, not zeners

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