No, it doesn’t subscribe you to anything.
It wouldn’t be compatible with SSO enabled, same as things like social logins.
Thinking about this some more though, it might not be worth the hassle for the user. We’d have to require a confirmation mail, otherwise anyone can vote on your behalf willy-nilly. After first confirmation maybe we could keep that in a cookie and let the user spend their TL0 votes without confirming again, but that’s a lot of added complexity for such a simple feature.
The pondering continues 
That would indeed be a whole lot simpler and would be a great first take in any case. I could swear this was discussed elsewhere at some point. Anyhow, I’m all for it.