Thanks to Sudra, there's now an easy way to "mask" spoilers within your posts to the forum. Simply enclose the text that's a spoiler within the "spoiler" BBCode tag, like this:
Soylent green is people!
This looks like:
To view the spoiler text, just use your mouse to highlight the black box, and it will show up. Please do note that this doesn't change the board policies on spoilers.