Cherry-picking details is the quintessential form of editorializing. See
https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que... for more.
Let's look at your further examples.
1. Re "PIA (PrivateInternetAccess) VPN bought by company known for distributing malware", that one was outrageously editorialized. This is a complicated case though, because we often allow changed titles when the article is a corporate press release. Companies tend to use bland nothing-to-see-here language that can be misleading in its own right. But "bought by company known for distributing malware" is a massive claim and we have no idea whether it's true. We're in no position to adjudicate the truth or falsehood of everything people put in titles. So in this case, both choices were bad: the editorialized title as well as the bland original. If we could have come up with a better (i.e. accurate and neutral) title, we would have used it. But it wasn't obvious how to do that, so we went with the lesser evil of the original title. (We also got an email complaining about the editorialized title, but the complaint didn't cause us to change it, it just caused us to take a closer look.)
As for the acronym, it would exceed the 80 char limit to expand it in the title, so I didn't. Also, "Private Internet Access" is so generic a phrase that I'm not sure it's all that clarifying. Anyone who would know what that phrase means in this context would already know what PIA stands for. For those who don't, it would only take a tiny bit work to find out, and it's not a bad thing for readers to have to work a little. https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu.... One more thing, too: when an acronym is used in a title unexpanded (e.g. "CS", "AWS", "AMA"), it often contains the subtle additional information that the acronym is a widely-used one in the community, which PIA is: https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu.... So in this case I'd say the acronym was a wash. By the way, we really do consider all these details when weighing how to edit a title, and since I was the moderator in this case I can tell I did that; more, even—but this answer is already too long.
2. We've learned from long experience that science articles lead to shallow, angry arguments when their titles make excessive claims. Instead of talking about the actual finding, the threads fill up with objections to how overstated the title is, and (worse) generic ventings about title inaccuracy and the decline of journalism and western civilization. In other words, such titles are baity.
We've learned that the best way to de-bait them is simply to narrow their scope, i.e. shrink the title down to the size of the real story. In this case we applied two scope-narrowers: "in mice", which is a great de-baiter when the story is about a mouse study, and ": study", which makes it clear that the topic is just a study, not the god's-lips-to-your-ears revelation that headline writers love to imply. Basically, it's their job to sex up the title and our job to knock it down to size. Those two devices work well for preventing science-article threads from going off track in predictable ways.
---
I know all of this can appear inconsistent, but that's because there's so much more going on, so many more concerns and details than one would ever imagine in the title-editing domain. For the first few years I did this job I used to find that irritating—how can an issue as trivial as internet titles be so important? Over time I learned how much more there is to it. I wrote about this here if anyone is interested: https://news.ycombinator.com/item?id=20429573.
The one thing I feel most comfortable defending about all this is how consistent we are—not completely consistent, but for sure relatively. You may not agree with the principles and that's fine, but we're not applying them arbitrarily. A nice aspect of the job is that we don't have to apply them arbitrarily: we have a good set of principles to rely on and they cover most of what comes up. We could talk for the rest of the year about specific cases and why exactly we edited them the way we did. But it all comes down to the site guidelines and the fact that intellectual curiosity is the organizing value of this site.