I have a StackExchange login that I use for all the communities that I'm a member of. If I visit a community that I am not a member of, the title bar shows a link. Clicking it brings up a "CONFIRM YOUR NEW ACCOUNT" page:
Clicking the button automatically adds me to the community. Nice and easy.
But, if I'm looking at questions in a community where I'm not a member, and try clicking the "Upvote" button for a question, things will get very complex. First is a popup prompting me to sign up or log in:
Since I do not yet have an account to log into, I'll click the "Sign up using Stack Exchange" link (the other options are "Sign up using Google" and "Sign up using Facebook").
This will bring me to another page with the same "Sign Up" options as before, except under "Sign up using Stack Exchange" there are four text fields to be filled in: name, email, password, and password again:
Filling out all four fields works, but why the complexity? Why isn't the first "Sign up using Stack Exchange" link the same as the link? (BTW, clicking "log in" on the first popup window is just like clicking the link, which is also confusing because I shouldn't be able to "log in" to an account that doesn't yet exist.)