This behaviour might have changed; I have just posted multple polls in a single post. I got this weird error message:
This also occurs here in meta.
That suggestion is quite meaningless to the average user, and has likely become a bit scrambled due to the HTML not being recognised.
May I suggest this text instead?
An error occurred: There are multiple polls without discreet names. Use the name attribute to uniquely identify your polls like this: [poll name=poll1 type=regular]
