PP cookies: .mydomain.com
Login on PP and you're signed in on PP but not xF
Login on xF and you're signed in on PP & xF
Logout on PP and it does NOT log you out of either.
Logout on xF and you're logged out with both.
To make it worse, some (not all) can't login on either PP or xF and then be logged in on PP. Washington Fly Fishing