i placed a poll in this story here, but it's is not possible, to place a comment there.

I guess that has nothing to do with the poll. I guess you edited your story editor template today. I guess that when something worked not as expected, your mind said "it's the poll" because that's what it was thinking about in that precise moment, instead of saying "it's the story editor form".

Generally, that's how human minds work. But of course I could be wrong. How many points do I get?

I used this occasion to fix the problem. All I had to do was to set res.data.action in comment/create.hac and story.commentform_macro().

PS: I think using a separate skin parameter would have been a better idea than to putting the form action into res.data.action. Even though it isn't a serious problem since scripts can overwrite the parameter when it's their term.