HN readers' parents are likely far more technically inclined than an average person.
(The commenter did not invoke their own parents, which might be a slightly more reasonable position)
Making a claim that HN's parents must be technically incompetent adds nothing to the thread, is likely to cause momentary confusion, and only contributes to the "bad" ageism that you are concerned about.
I'd rather say: it's wrong.
HN readers' parents are likely far more technically inclined than an average person.
(The commenter did not invoke their own parents, which might be a slightly more reasonable position)
Making a claim that HN's parents must be technically incompetent adds nothing to the thread, is likely to cause momentary confusion, and only contributes to the "bad" ageism that you are concerned about.