It’s a pain in the backside, but if you lodge a request, then you can get the incorrectly charged fare refunded:

http://wongm.com/2012/07/getting-myki-to-refund-incorrectly-charged-fares/

None that in the case of Sunbury, if you travel from zone 1 and don’t touch off, the default fare should be the same as the fare charged if you did touch off:

http://www.danielbowen.com/2012/03/27/myki-myths-2-touch-off/

Fascinating stuff. Thank you for the info! I don’t think one of those breakdowns you mentioned would be tolerated by passengers on the MTR, especially given the problems they have recently been running into. The only problem I’ve ever had with my Octopus card at one of those gates was around 2011 when I was on holiday in HK and the gate wouldn’t let me in for some reason and that was fixed very quickly by a friendly member of staff who told me to wait a few seconds and try again after resetting something on the computer terminal.

Melbourne’s myki gates were supplied by a company called Gunnebo:

https://railgallery.wongm.com/myki/E118_1675.jpg.html

They also supplied 516 flap gates for the KCR in Hong Kong:

http://www.railway-technology.com/contractors/station/gunnebo2/gunnebo21.html

Those gates appear to have been installed on the newer Ma On Shan and West Rail lines, as well as retrofitted to other MTR stations to permit wheelchair access.