Gift is reversible also, everything on paypal is.
On a slightly unrelated note, how can you do any sort of business using paypal?
You could ship some physical goods over to users and they could then ask for a charge back.
Is there no sort of protection that bit coin dealers could use?
FFMG
Trading currencies via PayPal is against PayPal law.
So, no. There's no safe way to do it.