At the request of @dystopianfuturetoday, who has recently been posting some interesting riddles in his blog, we've added support for concealing spoilers in your comments.

Simply surround your spoiler text with the tags <spoiler> and </spoiler> and it will be invisible when your comment is displayed. It can be made visible either by selecting all the text on the page (e.g., CTRL+A) or by click-dragging using your mouse over the hidden text.

Give it a shot!