The HN guidelines (edit: which are at https://news.ycombinator.com/newsguidelines.html and linked at the bottom of every page) say not to use the original title when it is misleading or linkbait. How could that be clearer?

Do we judge every case correctly? Good lord no. That's why we change things when people point out our mistakes. The community contribution here is considerable, so the best way to complain about a title is to suggest a better one.

The guideline also explains why titles can't be automated in the way you suggest: the software would have to identify what is misleading or linkbait. If anyone can show us such software, believe me, no one would use it more eagerly.

I'm glad HN is like this. It's one of the reasons I enjoy the website.

It might be convenient if HN had a tool like reddit to automatically fetch the title from HTML given a URL. In fact, if they had such a tool, I'd expect HN to maybe actually mandatorily make that the title and not allow you to edit it, since it seems to be HN editorial preferences not to let submitters write titles.

This was tried, I think. It was proven to be a bad idea in practice. If you think the complaints about titles were bad now, you should've seen them when the software did automated reversions. At least, I think they were automated reversions.

Sometimes the subtitle is a better title. Sometimes the original title is clickbaity, as you said. Regardless, it takes a person to moderate the titles.