Firefox blocks this extension.
I have uninstalled and reinstalled, but no luck.

developer sold out to avast

"This extension hides automatic sign-in pop-ups on Youtube."

Not any more it doesn't. It worked once, on first use, and hasn't hidden the sign-in nag since.
Uninstalled.

No more YouTube sign-in prompts.

EDIT: mishap descibed below happened only once
with add-on installed and on, i still got the sign in popup. i'll try to monitor if it's happenning regularly