MMO limit is 0.82. The QRH basicly says to reduce speed if the speed is above VMO(340)/MMO. It would be a mandatory techlog entry and i would write a report afterwards as well.
Anyway, personally i do not like to use VNAV when more than a couple 100 feet above path because exactly this scenario can happen despite my fleetmanager telling me that flying VNAV has more protections than using simple airmanship. Level change with a slightly higher descent speed usually sorts out the tailwind and above path situation, if needed i can take the speedbrake as well. Approaching the path i can switch then back to VNAV. VNAV usually tries to aggressively recapture the path with up to MMO/VMO and with an additional sudden increase in tailwind you can easily bust the limit which is not really a nice thing.
The measures taken seem pretty harsh though.