>>Never submit negative feedback via "anonymous" or "confidential" feedback processes at work
Never give feedback at work, unless positive. This includes things like code review.
The dirty little secret of human relationships is every one wants to be made to feel special, error less and look good. Only thing any kind of feed back, correction or criticism leads to is rivalry/enmity, and it won't end well. The question is not if some thing like that happens, but to what degree.
There are stories going back to the time of Abraham Lincoln, where he refuses to even criticize big mistakes made by generals during the civil war. If that is what some one in the position of Abe Lincoln, in a matter as serious as Civil war did, your code review feedback can wait. Nothing productive ever comes out of these processes.
If you absolutely have to display allegiance to political cartels at work. Wait until a clear leadership superiority is established, Meanwhile use silence and smile as a strategic activity to avoid getting shafted.
There can be no friends at work. In stack ranked systems, with subjective evaluation. You need to follow the Kissinger doctrine. No permanent friends or enemies only allies based on interest that serves you.
Seen too much of this to realize to leave people/systems on their own.