I'm not sure how hard it would be to program a feature like this into the site but I have seen it on other forums and thought it would be a great addition to posts on NA.
If their was a tab on the top tool bar for hidding your post as a spoiler, so posts would only appear as "click for spoiler" in a thread. Then when clicked it would reveal the post.

You could use the text background tool in the compose window.   <---- highlight to read
Spoiler: It was Dr Wily all along!

edit: Or use white text.  <---- highlight to read
Spoiler: our princess is in another castle

Just a workaround for the time being.

Lol never knew you could do that.
 

Thats a really good idea and solution gunpei, but I don't think most folks would think to use that method.

Like I said, just a suggestion for a workaround, if someone really wants to do it before the feature request is implemented (if ever.) If it is, tags could be based on that, as a simple way for Dain to build it. In the meantime, if people see it here and there, the idea could spread ¯\_(ツ)_/¯