Also, the spoiler is shown on a simple mouseover. I could imagine that a single word or phrase can be unintentionally read with an accidental mouseover.
Who did it? The butler!
Also, at least on Safari, scrolling the page so that the spoiler meets the mouse position reveals it as well. If the target is large like an image, this is a likely accident!
Finally, I’m not sure how this would work on a touch interface, since there is no mouseover equivalent. This should require a click to reveal (and perhaps re-hide) the spoiler. The appearance should probably also provide more indication other that simply a redacted appearance.
A folding block would probably solve this…
Edit: I just noticed that the spoiler text shows on the activity-tracking pages as well. If I bookmark something so I can read it when it will no longer be a spoiler (i.e., I’ll want to read it after I’ve seen the new episode), then go to my bookmarks page before i’ve seen it, I might see the spoiler.