This is one of the more bizarre auto-editing of titles it does because of how pointless it feels.
"The man who" is established English convention. "A man who" is changing the meaning for the sake of it without producing a clearer title. The person is unambiguously defined, so the definitive article is entirely correct. If the person isn't one of a set of people to whom the description could apply, it makes no sense to use the indefinite article. If a title was, "The man who starts every day with steak and chips" then switching to, "A man who starts every day with steak and chips" feels correct, he almost surely is not alone in doing so.
In contrast, "A man who coined the word Robot", is not correct, it alters the meaning to suggest that someone else could also have coined the word.
HN also removes "How" from the start of titles which often destroys meaning too. That is explained as trying to "reduce clickbait" titles, but the effect is often to make the title nonsensical.
It's one of the many contradictions about this place.
I feels as if whoever set up this system hasn't truly understood the meaning that "The man who" conveys, and has attempted to force a version they see as "more correct" despite it producing nonsense.
Fits with the 'robot' theme
Like, if you have an infinite mana combo, you can just keep running the steps of it to block gameplay instead of playing your fireball
Operations:
1) Split an integer into two smaller integers. (e.g. [7, 5, 3] → [6, 1, 5, 3]) 2) Combine (add) two integers into a larger one. (e.g. reverse the last e.g.)
Restrictions:
1) You can never make an integer greater than the largest integer in the original list. 2) You can never make a move that results in the same integer appearing in the list more than once.