This is a chronotransponder. A silent one.
You can write posts from here. SilentBot will deliver them. Silently.
You click the "Write a post
You will see a post editor similar to the one in the real OTT. With some exceptions.
You can define when
the post will be delivered. Use the Time: Y, M, D and H fields.
You only have one post per hour. If you add a post which has the same username, password and post time it will replace the previous one.
You have to enter your xkcd username and password.
You have some option checkboxen on the bottom. One is new.
If you select this SilentBot will be very silent and won't add "posted by SilentBot" to your post.
The list of messages. It's empty. But if you enter your username and password and click "Reload list" all posts with your username and password will appear there. You can view, qoute, edit or remove them then.
You can also use the file upload interface. It's explained in this post