Not demonising the seller by using your rights as a buyer.... no your not....
Filing a claim against a seller without a first point of contact is.... you should
always attempt to sort a problem out with the seller first before making rash decisions.
I'm also a power seller and sick annd tired of people going straight to the paypal resolution center if they have a problem when they could have contacted me first!
You answered your own question huh.
Even if the seller states they don't accept returns, as others have said it doesn't necessarily mean they won't. It may just be an oversight writing that.
As others have said:
Your covered for 45 days after the purchase so if your unable to resolve a problem with the seller your still protectioned through the arse.