It works. But there is very limited control on extension behaviour and the only sign in option that works with the extension is username + password. If you use a linked account to sign in there will be a signin popup, but the extension ultimately does not recognize it. There is limited interface for feedback too.

Stops you from supporting Israel, and the murder of innocent children

Early days I think. I really hope it gets better as it's so cute and a good thing. but seems like the data needs to be populated first. I put in some really obvious things which should have been flagged but were okay (you can submit a form to indicate that the results weren't right). Great this is in the works but perhaps for now rely on your own boycott guides.