can vote in multiple-choice poll many times

The fact that the Enter key performs the action of the Submit button means that you can vote on a multiple-choice poll, come back to the screen again, check more boxes, and hit the Enter key to vote again, despite the absence of the Submit button onscreen.  At least you can in Firefox.  I don't use IE, so I'm not sure about that browser.

a) you are probably already aware of this, and 

b) I have a feeling the polling code is not custom, and

c) it's not the end of the world

so this may or may not be important.