Hi! I saw that nobody has replied to your post about this yet, and while I'm not one to like collaborative writing, I wanted to direct you to some different sources on the site that do have this and ones that'll probably get a person to write with you faster than just a forum post. There is the Double-Trouble Writing Roulette which is apart of the Storybook forums where you can find a writing partner. Not only this, but there's clubs/1952/forum which is similar to the last one I linked. And finally there's the Storybook section in itself which has to do with many people collaborative writing. I hope you succeed in finding a writing partner!
One of the things I love about YWS is the quote generator. For example, I'm reading a really serious work, and then I see "Moo. - cow" at the bottom of the page. — Darlet