The guidelines at http://ycombinator.com/newsguidelines.html state: "You can make up a new title if you want, but if you put gratuitous editorial spin on it, the editors may rewrite it." but this should not apply just because the title submitted does not match the article. When the actual article's title makes no sense or provides no context, it should be allowed to stay changed.
A story is currently on the front page with a title of "Where the Heat and the Thunder Hit Their Shots" which was just changed from its previously edited title of something about visualization.
"Where the Heat and Thunder Hit Their Shots", while actually the title of the article, says absolutely nothing about the content of the article. Is this an article about weather? Photography? Nope, it's about basketball. Why is it on Hacker News? Oh, the submitter liked the visualizations, which is exactly what the previously edited title said before it was changed.
Another example: https://news.ycombinator.com/item?id=3875857 was a story about Light Table and the title was edited to reflect that until it had at least 100 points. Then a moderator changed it to the story's actual title of "On concepts and realities" which said absolutely nothing about it and probably caused lots of people that had already visited the link once to read it and think it was something else.
Moderators, please stop doing this.