There were 15 participants in the GitHub issue. Hardly enough people to manipulate anything, so obviously that was not the intention. Even though some 300 people are watching the repo as a whole I doubt that many of them would see that particular comment. As the parent to your comment said, a screenshot is a reasonable way to inform the others in the thread that the link has been posted.

I am against vote-manipulation of course but I don't think that this is an instance of it.

This thread has 71 points in 3 hours. Having 15 people upvote it all at once could get it onto the front page, where it then keep getting upvoted naturally.