Yes, voting and commenting require an account. Browsing posts can be done anonymously.
Without accounts, vote stuffing destroys the signal. Each vote represents one identifiable person, which is what makes the resulting prioritization useful.
Low. Customers can:
ProductLiftIdentify({ email, uid, name, ... }). No login screen. See Single sign-on (SSO).The SSO path is what most customers use in production. The customer never sees a login screen, they're identified from your app.
Browsing yes, posting no by default. There are alternatives if you need anonymous-style feedback:
See Privacy & anonymous posting for the full picture.