Recently during code review, my direct supervisor wrote a comment suggesting a change on some code I submitted. Normally, that is not a problem (and I understand that is the very point of code reviews), but it turns out that his concern is based on incorrect information.
More specifically, he raised concerns over a certain language feature, and explained why that could be an issue - except that, in fact, the language does not work as he explained. This is supported by language documentation, and is not a formatting/standards issue. (The language issue is about as complex to understand, simple to fix, and makes as much of a difference as a trailing comma in a C array. That is to say, this behavior has never been changed, it is not hard to grasp that the comma is optional, it is not an obscure concept, and it does absolutely nothing. I'm keeping the exact issue a bit vague on purpose.)
My question, then, is how do I explain to him (if at all) that his idea of how the language works is incorrect? Being at least one or two decades junior to him, I don't want to come off as arrogant. I would normally have no problem with sucking it up and making the change (it's as easy as deleting a comma) - but I also feel like that goes against the spirit of a code review.
Not a duplicate of How do I tell a coworker he's wrong?, since this is specifically about telling your seniors they are wrong..