I noticed this on Try Discourse. The poll tells me I must be trust_level_0 to participate.
I think a more meaningful, user-friendly message would be that users must be logged in. My understanding is that it isn’t possible to dip below UTL 0, so if they don’t have a UTL of at least 0, it means they’re logged-out / not registered. Though I’m not sure if any message is required at all - I wouldn’t expect to be able to participate in a poll on a forum if not logged-in.
Screenie;
As an aside, @awesomerobot’s profile over there seems to be in a weird state; it perennially claims to have joined (and other things) “just now” - as if the data is either missing or somehow invalid.