How to protect a MAX232 from PIC programming high voltages?
You could interface the MAX233 to the MCU using an Open Drain or Open Collector arrangement.

The MAX233 activates a transistor (NPN BJT or N-channel MOSFET) which in turn pulls the MCLR pin low.







simulate this circuit &ndash; Schematic created using CircuitLab

This is also one of the recommended ways of activating a reset line from multiple sources - a wired or arrangement using open drain devices.

Note that the logic of the reset is then inverted from the perspective of the MAX223 - you need to set the output HIGH to pull the MCLR LOW.