Employee review system is compromised - Software Engineer II Canonical Employee Review

The review system is lauded internally as very sophisticated (I heard that the CEO tried to make money from it somehow) and occurs every six months, which I find too frequent. It is anxiety-producing because you're evaluated by many people in the company, potentially from anyone, even those who have no idea what you actually do. The result is a collection of anonymous dots on a graph, grouped by category of peers. If you somehow end up in the bottom portion of the graph the company policy is for your manager to put you on the dreaded "PIP" (Professional Improvement Plan"). If you refuse you will be let go with a run-of-the-mill severance package. If you accept, and succeed (after six months), you will stay on to live another day. If you accept and fail you will be let go without severance. Many people I've talked to in the company have figured out that the system does not give accurate results. Either there is corruption due to quid-quo-pro agreements, or there is deliberate malicious poisoning from colleagues who do not like you personally, or simple popularity contest results, or worse of all, good results are ignored, even when those results are provided by one's own manager. One person got good results on the graph, and even specifically from their own manager yet a few weeks later was presented with the described ultimatum. Then there are the ones that are personally liked by Directors yet whose work is bland and end up getting significant salary hikes or having special roles created for them. This company becomes stranger and stranger as it moves closer to its IPO. It's to be avoided if you are at all sensitive to a bad employee compensation system. However, if you believe yourself to be a "top performer" then you may like it very much here as the company cherishes "technical champions". Personally I find it all very tiresome and unprofessional. I don't see myself still here in two years time.