So many noob mistakes in the UI and I haven't even started using the site proper.
I see a link "Create Community", this takes me to a form where I get to create a community. I spend time naming and describing this community, and then click the Submit button. At this point it decides to tell me that I need to use lowercase for the community name.
So I fix that and hit Submit again. At this point I'm told I have to create an account first. WTF, why didn't you tell me earlier? If I leave this page to create an account, will you preserve what I've filled into this form for when I get back? Why didn't you just add the necessary username/password fields to this form at the same time you showed me the error?
Anyway, so I click on the link that says Login/Signup and get a popup that says "Are you sure you want to leave?" Now I have to click again to remove this popup. Another wasted click and +1 to the "annoyed" meter. See above for how this could have been avoided by just adding the login/signup forms to the form I just filled out to reduce friction.
Anyway, so I create an account. And it turns out the site forgot everything I'd done before that. Why ask me questions (make me fill out a "Create community" form) if you're going to immediately forget all my answers?
Absolutely no respect for the users time. Why would you do that when your very existence depends on attracting more users?