My take on this: You're absolutely allowed to speak on your experience, but you should also take the feedback at face value and try to figure out whether it's useful or not. Plenty of feedback here on HN is good, but of course there's also plenty that misses the mark.

That being said, an ADHD diagnosis at the age of 2 goes against all current best practices, so it might be good to revisit the subject and ask to be evaluated again.

Even in the likely case that it's confirmed, you might get additional support, advice or diagnoses that can help you in the future.

I wouldn't take it so personally when someone disagrees with you and downvotes you.