I too find Discourse polls to be less intuitive than they could be. When first confronted with one I had no idea that it was a poll at all. The tweaks suggested by the topic poster would help mitigate the issues, but it would be better if the standard inputs would be used, as provided by the web browser.
Also, I think it would be better if the “submit” button would be located directly under the options list (instead of below the line) and that a label such as “Cast vote” would be better.