- text is nearly unreadable - there's no separation for any of the posts. no rankings, you can't visually separate elements within the post. there are too many of them on there -- which do I read first? Should I read them all, or just the top one? Are they in some sort of order? A visual redesign will help will all these things. - Can I post w/o creating an account? I hate creating an account places. Why do I need to do that? It's not obvious that I need to create an account to post. - Who are these people? Are they users, or celebrities? Is this their twitter feed?
I'd focus on visual design. You don't really have too much "usability" that's very complex.