Yes, people do that sometimes, perhaps with the intention of giving an intro to the article and maybe not realizing that it comes across as promotional.
FWIW this submitter is definitely a legit HN user - we've been in contact via email - and this is a good article!
I did not interpret it as promotional. The text of the comments was so non-sequitur that I believed the account to be a straight-up bot account, posting random snippets from articles. It was only when I investigated further, when I saw that the same user also submitted all the articles, that I started to doubt my initial impression.
FWIW this submitter is definitely a legit HN user - we've been in contact via email - and this is a good article!