Looked up the 18F4550, and it's not better.

Voltage on MCLR with respect to VSS (Note 2) .......................... 0V to +13.25V

Note 2: ... a series resistor of 50-100Ω should be used when applying a “low” level to the MCLR/VPP/RE3 pin, rather than pulling this pin directly to VSS.

Maybe I've just been lucky, or my PK4 has a thing against 16F pics.

Either way, a little prevention added to my circuits shouldn't hurt; like a zener on MCLR, and 50-100R when pulled low.

Robert