Thanks @pfaffman. I checked this again, and it appears:
Correct: regular topics (with polls) redirect back to the topic after an existing user logs in. No issues there.
But: unlisted topics (with polls) redirect back to the home page after an existing user logs in. So slight edge case here but would be nice to redirect user back to the unlisted topic.
Still an issue: would like new registrations to return user to the topic (with poll) as it does for groups in the linked topic. Currently, new registrations are redirected to the home page (unless you have the
redirect users to top page setting enabled).
Not sure if a topic (with poll) being unlisted complicates things but would be nice to at least cover the registration scenario.
The Reply button on a normal topic has the same behavior for new registrations–>users are returned to the home page instead of the topic where they hit the Reply button.
Not the end of the world, but would be nice to avoid the reaction for a new registered user: “What just happened?” or “Where was I?”