I think I disagree with everything here.

Exceptions Are Much Easier to Work With

Well, they're "easier" in the same way that dynamic typing is easier. It's obviously less work initially just to say "screw it; any error gets caught in main()". But that's short term easiness. In the long term its much more painful because:

1. You don't know which functions might produce errors, and therefore you don't know where you should be even trying to handle errors. (Checked exceptions are the answer here but they are relatively rarely used in practice.)
2. Actually handling errors properly often involves responding to errors from individual function calls - at least adding human readable context to them. That is stupidly tedious with exceptions. Every line turns into 5. Sometime it makes the code extremely awkward:

try {
   int& foo = bar();
} catch (...) {
   std::cout << "bar failed, try ...\n";
   return nullopt;
}
foo = 5;

(It actually gets worse than that but I can't think of a good example.)

Over 100× less code! [fewer exception catching in their C++ database than error handling in a Go database]

Well... I'm guessing your codebase is a lot smaller than the other one for a start, and you're comparing with Go which is kind of worst case... But anyway this kind of proves my point! You only actually have proper error handling in 140 places - apparently mostly in tests. In other words you just throw all exceptions to main().

System errors [he's mainly talking about OOM, stack overflow & arithmetic errors like integer overflow]

Kind of a fair point I guess. I dunno how you can reasonably stack overflows without exceptions. But guess what - Rust does have panic!() for that, and you can catch panics. I'd say that's one of the few reasonable cases to use catch_unwind.

Exceptions Lead to Better Error Messages

Hahahahahaha. I dunno if a bare stack trace with NullPointerException counts as a "better error message". Ridiculous.

Exceptions Are More Performant

Sure maybe in error handling microbenchmarks, or particularly extreme examples. In real world code it clearly makes little difference. Certainly not enough to choose an inferior error handling system.

I would say one real reason to prefer exceptions over Result<>s is they are a fair bit easier to debug because you can just break on throw. That's tricky with Result<> because creating a Err is not necessarily an error. At least I have not found a way to "break on Err". You can break on unwrap() but that is usually after the stack has been unwound quite a bit and you lose all context.