I don't know that there is a huge difference between those two. What I do know is that in this case there was no difference of any significance.

The comment was signed with his username, and his Docker affiliation was disclosed under said username. That was all that was needed to add validity to the claims in the comment.

All HN comments have that "generic signature". All HN users are free to disclose information about themselves on their profile, and all HN readers are free to click usernames to learn more about the the people who comment on HN.

It really is that simple.