Hi and thank you for this plugin!
Since this annoying bug is still not fix I will have to post it again:
The sidebar’s html in the twenty-fifteen theme is before the actual content and the registration form. So if a user clicks on the activation link in his or hers email the message:
“Your account is now active”
is displayed only in the sidebar’s login widget.
The content shows:
“You are already activate”.
(which btw contains a typo, too)
This is the result of the code in login_form line 141.
Please fix this. It should be easy.