Post preview

[RogerDodger]

For JS enabled users, beside the "Post comment" button should be a "Preview" button.

When clicked, the "Preview" button should be replaced with a "Please wait..." button and the textarea should be dimmed. The post's body is sent as an AJAX request to the server which returns the post render. Once received, the post render replaces the textarea, and the "Please wait..." button is replaced with an "Edit comment" button. The post render should behave exactly like an ordinary post in the thread (that is, hovering >>RogerDodger quotes should work as expected). The "Edit comment" button when clicked removes the render and returns the textarea. At all times the "Post comment" button should behave as normal.