Unfortunately this sort of things happen at many airlines, not unique to TK.

I have been bumped from a confirmed upgrade to Executive First on AC Latitude ticket. AC claimed that they do not oversell but they swap equipment! Adding insult to injury, the last J seat was given to an AC employee.

Reward ticket in SQ business class - my pre-assigned seat was given to one of their PPS members and I was unceremoniously given a middle seat in the centre section. (SQ's regional J configuration is 2x3x2.)

At least, SQ was willing give me some Krisflyer points for the "inconvenience" but I do not collect Krisflyer points. It was moot. AC? Nothing, nothing and nothing. Standard reply that they have the right to do so. Several years later, it still left a bad taste in my mouth. AC has won the battle but it has not yet won the war.