> Ethically, this situation has some similarities to the DAO fork.


Much better analogy:

1. An ISV make software which makes use of an undocumented OS feature.
2. That feature is no longer present in the next OS release.
3. ISV suffers losses because its software cannot work under new OS, and
thus people stop buying it.

I think 99% of programmers would agree that this loss was inflicted by a
bad decision of ISV, and not by OS vendor changing OS internals. Relying on
undocumented features is something you do on your own risk.

I think it is ethically unambiguous to everyone who isn't on Bitmain's
payroll.