Since the poll feature only allows a single poll per topic, I just had to create one larger poll. I created it, edited the topic (which by the way refreshes the topic without the poll visible) and after a while I grew my responses from eight to nine.
Turns out the poll only allows eight responses and will simply discard anything beyond that number without informing the user that this happened. Not a great user experience.
I also have to ask if the poll plugin is supposed to be a first class feature, since it is still nowhere visible in the UI.