FYI there's no such thing as direct messages on HN.
You need to put a means of contact in your profile, or edit your comment to add it. It can be a disposable e-mail (like https://temp-mail.org/en/) if you want to enable a short-term communication like in this case.
(Side note, I've seen this crop up so much that it kind of seems like it would be good to have a DM functionality in HN, even if messages were auto-deleted after 7 days or something, or if it just forwarded to a non-public e-mail address.)
