Show proper error for invalid passwords.
I'm not sure if the password requirements (for mobile login) are very simple, but they're not documented, and when you try to set one you just get 'invalid password'.
That's either a UX bug or a documentation. But since there's not really any good reason not to allow complex passwords, I'm going to guess it's a UI bug.
It’s already stated on the right side of password field (“must be non-empty”).
And I’ve just duplicated it in the error text too. Thank you for the idea!
Thank you for information. I'll try to improve handling of passwords filled in by JS.
Dan Boger commented
Oh, I see what happened there. I had the password filled in by JS, so your JS password verification never got triggered, so it never noticed it wasn't empty. Perhaps you could have it trigger on hitting 'submit' as well as on keystroke?