@stormy I have searched the site for "polygonum" and found a question where your answer has a negative score, is this the one gardening.stackexchange.com/questions/9556/… ? I see it is tagged under "identification", so I guess somebody saw the question and disagreed with your ID.

@stormy If you have more than one downvote on the same question, it might be that the plant is a trending topic somewhere in the world and multiple users searched for it.