Twitter currently forces you to express your entire thought in 140 characters. Or, at most, in some small multiple of 140-character posts. Usually the friction of splitting something out like that caps people at around 3 posts.
Your "self post" style idea with hidden "embedded text" would only really force people to be concise with what effectively become the "titles" of their rambling, hidden, posts. It does nothing to solve any of the problems created when you lift the arbitrary conciseness limit; the manner in which people express ideas gets flabby when they have infinite space in which to express them.
I don't want a timeline full of titles to posts I'm rarely going to click into. That's a big decrease in the value Twitter is providing to me.
A lot of the posts in my stream contain links to images, videos, and articles. In a sense, the 140 characters (minus the 20 required for a url) already are a title for something more time consuming. I'm not sure that hosting self posts would really change that, it just makes it easier. Instead of linking to my blog post, I link to a twitter provided long post.
Your "self post" style idea with hidden "embedded text" would only really force people to be concise with what effectively become the "titles" of their rambling, hidden, posts. It does nothing to solve any of the problems created when you lift the arbitrary conciseness limit; the manner in which people express ideas gets flabby when they have infinite space in which to express them.
I don't want a timeline full of titles to posts I'm rarely going to click into. That's a big decrease in the value Twitter is providing to me.