> Is this Reddit?

You've asked this several times and it will attract downvotes every time as it's against the guidelines. People have been worried about HN "becoming like Reddit" since soon after it launched over 10 years ago.

People generally downvote because they don't find the comment convincing or enlightening.

Downvotes are less likely when commenters explain their position with thoughtfulness and effort to help the community understand and learn things.

This post is answering a specific question and is delivering a citation for it. As far as I can evaluate, the source is accurate.

Why is it flagged? What do i miss here?

The post is probably automatically flagged because it's a new user and he has been largely downvoted in his other comments.

You can vouch for it if you think the comment has its place here.

(edit I don't have the "vouch" option, so maybe the comment has been downvoted as well, but it doesn't appear grey to me so I'm not sure).