I guess that makes sense. Based on my math lectures during college, mathematicians can often be terrible at communication to other humans, so that would explain why they think what they said is different from how pretty much everyone else reads it.

User names match... are you the original author? Why commenting in the third person?

Apparently the mathematician author doesn't understand the meaning of his own natural language quantifiers. “it is not in general possible to find bugs by examining the code” means “it is not in general possible to find ANY bugs by examining the code”, not “it is not in general possible to find ALL bugs by examining the code”.

And the first interpretation is relevant but wrong, whereas the second interpretation is true but irrelevant.

P.S. It seems that the author meant to say “it is not in general possible to find a given bug by examining the code”, i.e., "not (for all bugs B it is possible to find B)", which again is true but not relevant.

Ofc you're correct in that sense.

I would add that (related to your "maintainability" point) ensuring the code is as simple as possible, and thus much more likely to be "debuggable by review", is a goal of review. Even that won't prevent bugs in the absolute sense, as you rightly say, but it boosts your probabilities.