I edited this question's title (Death Note spoiler) to avoid spoilers. Later on, it was rolled back. Should I not have edited it then?
I'm not quite sure that the title is needed to contain such spoiler. The fact that it is tagged as Death Note seems sufficient to suggest who is meant by 'shinigami' and 'character'. Besides you can always type the real question in the post. This can still be searchable in google afaik.
So if the question is
Why did John kill Jane?
, then why not have the title be something that censors (at least 1 of) the names like
Why did X kill Y?
and then just say the real question in the post.
If this title isn't informative enough, then perhaps we can say the episode title/chapter or the season or volume. Eg
Why did X kill Y in S02E04 ?
or (in case that would be a spoiler)
Why did X kill Y in this season 2 episode ?
I happen to know in other sites like reddit or myanimelist, it is extremely forbidden to put a spoiler in the title. This isn't just for anime but other for other fiction subreddits/forums and even for, like, sports or gaming subreddits/forums.
'A good title is always more important then avoiding spoilers' would be completely nonsensical there. They even go a step further to say you should say what kind of spoiler you're hiding eg season X spoiler, manga spoiler, spoiler for another show, etc
Or maybe this is a stackexchange thing...What do movies se or scifi se do? Do they spoil people too?