[sirn]

I wonder if it's entirely unfair in this case. Custom firmware for 3D printers do not only brick the hardware, but can do real environmental damage (such as burning down the house[1][2]), so I don't think this approach is entirely unreasonable. It's not that uncommon to see someone modifying firmware to print material such as PEEK which requires 400c nozzle temperature, so this appendix could even be their legal protection for such cases (IANAL).

[1]: The most popular firmware, Marlin, has a feature called Thermal Runaway Protection which turned off the printer when it detected temperature has reached certain threshold. Prusa printers have TRP enabled by default, but some manufacture doesn't.

[2]: https://www.reddit.com/r/3Dprinting/comments/8ah96r/anet_a8_... this is about ANET A8, but flashing custom firmware with TRP disabled or with higher temperature limit may result in the similar situation (ANET A8 stock firmware don't have TRP enabled)

[cortesoft]

It might not brick the hardware, but it can get it to a state that makes it seem bricked to a non-expert user.

I think the fear would be that non-expert users would try to flash their custom firmware, run into issues, then try to get warranty relief claiming there is a hardware problem.

There would be no easy way for Prusa to tell whether the boot issue is actually a hardware problem covered by the warranty or a firmware issue caused by bad firmware being flashed.

They don't want to sign themselves up for having to assist users recovering from flashing their firmware.