I tried searching for similar incidents in the past[1], and I think the problem is that the title munging actually doesn't happen often enough for Hacker News to want to do anything about it. It's unusual that two front page articles were affected on the same day, but that's a small fraction compared to titles that passed through[2].
I don't know if Hacker News will pop up any extra confirmation to the submitter to warn that their submitted title were automatically edited, but I think that would be a better interface than relying on submitters and readers to fix the mistake after the article is already visible and ranked.
Whether any automated editing of titles actually helps with reducing clickbait is a different question.
It's an attempted technical solution to try to remove / limit the amount of "clickbait" in titles.
It does not work very well.