Alright, I seriously couldn't think of a title, so this will have to do.
Those spoiler tags can be quite nice, but the problem is, in something like the "Anime character who didn't deserve to die" or something like that, people just use the spoiler tag and don't say what they're spoiling.
I ended up spoiling a bit of Fullmetal Alchemist as a user didn't put down what they were spoiling. I was thinking as opposed to...

Black Mage is in SSF2.

Possibly make it a rule or a code to have to do something like this.

SSF2 Spoiler: Black Mage is in SSF2.

Makes things a lot easier if you don't want something you like unexpectedly spoiled.

The rule would be impossible to enforce due to the nature of the people who use this forum.

The code would be impossible to code due to the unlimited amount of choices for things that could be spoiled.

It is the user's responsibility to use the spoiler tags correctly, whether you are posting with spoiler tags or about to mouse over the spoilers. You can never be too safe and thus you must act accordingly, unless you're a dick and like spoiling things which I like to do sometimes.

An alternative to your problem would be to use the box tags to describe the kind of spoilers.
For example

I like the Box/Spoiler combo, but yeah overall this idea can't really be enforced. On any forum it's up to the individual to warn the other users what it is they are spoiling. Definitely contact a mod or admin though if you see someone blatantly spoiling something.