The preferred way to to indicate the level of spoilers is by means of adding a Header title to the section that has spoilers.
For example, if you view "Pilot"'s page, you can get a very good example where underneath the Synopsis, there are 3 Headings to indicate different levels of spoilers. There's a very basic and rough overview with no spoilers, then there's a Minor Spoiler entry, then there's an extremely detailed spoiler entry. All 3 entries are describing the same thing, but have different levels of spoilers to them, and can be skipped upon selecting a different heading or scrolling down fast enough.
If you have any further questions, feel free to ask me, the other admins, or the community at http://defiance.wikia.com/wiki/Defiance_Wiki_talk:Community_Portal or at our designated user pages.