> he has conflated single-step in situ debugging (which does in fact suffer from limited utility in the context of an OS kernel) with debugging writ large.

Where does he do this? The quote is only about single-step debugging.

> So as he rejected in situ debugging, he also implicitly rejected postmortem debugging and dynamic instrumentation

Do you have any evidence of this? It seems to me that dump traces and kernel probes have been an important part of Linux for many years.