A while back, a software change made it impossible to go back to the reply screen, once you had posted. That completely eliminated double-posts. 
Lately, though, a few double-posts have slipped in. One of the double-posters grumbled about his wireless setup.
Is WiFi the cause of the new double-posts?
Double posts never went away. The software just got better (but not perfect) at stopping them.
My theory is that if the server(s) are struggling then rare cases of double pressing the submit button will slip through the net.
I once posted about 7 simultaneous posts as a test. I think it was after the upgrade but Iām not sure.
Nice save 