Sellers adding for PayPal use is plainly BS

I never charge Paypal fees since the auction price is what I agree to anyway, and it seems to complicate things. I also charge a reasonable "flat fee" for shipping that covers most of the CONUS and if I'm off by a few bucks, so what? I control the whole thing by having a minimum price anyway, so alienating those who dislike Paypal fees seems like a bad idea.

Agreed. The seller controls all aspects of the transaction and should be willing to pick up the PP fees. If the seller accepts an offer then nothing really changes the calculus in my mind  about the seller picking up the PP fees.

Just offer what you are willing to pay for the product,shipping and Paypal. The seller is no more responsible than the buyer to pay fees. 

Actually I think you will find the seller IS responsible, after all they are getting the benefit of receiving payment IMMEDIATELY.  PayPal are not just going to give that service away.
Pretty sure it is in PayPal TOS that the seller should not try to pass on the fees to the buyer. Or words to that effect.
Better just for seller to never even,mention PayPal fees as it does cause many to just pass right away

I’m not sure I agree.  The buyer is getting the benefit of being protected and we all know PayPal tends to side with the buyer.  I usually offer PayPal and the option to send a check or money order.  You buyers sometimes need to take a leap of faith.  I’d rather wait for a check to clear any day than get paid immediately via PayPal.  And no, my items I sell are as I advertise so I don’t need PayPal, but some of you buyers do.