Hello, when perusing through the posts last year about LK99 event, I notice the thread (https://news.ycombinator.com/item?id=38691268) used a title other than original one.

Now that I am really new to HN mechanics, I am wondering how to decide which examples to follow. For example, despite the guideline statements, many threads around blog posts on HN actually use new titles.

Best to follow the guidelines (although you'll notice they mention a few occasions where the original title might be replaced - mostly for clickbait reasons).

For past stories, it's not always easy to tell what happened at the time. One of the other guidelines Please submit the original source. If a post reports on something found on another site, submit the latter can lead to a submission URL getting changed later without the title being updated (and so in retrospect the title doesn't seem to match).

In that particular case @wokwokwok did point out the submission had the wrong title, although perhaps they didn't email the mods to ask for a title update.

Some titles are either too long to use or are clickbait/inaccurate and need to be reworded

Thanks, but I simply quote "hint of near-room-temperature superconductivity" from the article. AFAIK the original title still contains too much details (the composition） for general audience on HN. Of course, the way I change the title will result in more clicks, so it could be "clickbait" in a way.

So how do I know that which title serves better? I'll appreciate the comments in this special case if it is hard to say in general.

Sorry, didn't realize that.