I don't understand why some sites refuse to allow tor users to log in. I can see why some might resent anonymity, but you aren't anonymous after you log in.
But my issue today is that I can't get a login form here on SE. I don't recall this happening before. New SE policy? Bug in the latest tor browser? Bug in SE?
Click a login link, browser shows all the visual characteristics of going to another page, but then refreshes the page I was already on. Sign up link works as expected, but I don't want a new account!