Lots of good points, so far. Here's my bit.
Like all things, certificates and rank have both negative and positive aspects. How this manifests in relation to you is your choice.
We have to "not care" or be attached to the idea of rank, and at the same time we must value it for what it really is.
Rank does not bring benefits, it should bring responsibilities. Promotion means that you should show a level of practice that matches the rank.
Teachers have not always awarded rank evenly and fairly. Some have even used rank as a carrot in front of students to gain money, emotional leverage, and even sexual favors. Rank in one system is usually not really recognized outside that system (sometimes not even within the same system!).
People get in disputes comparing and bickering over whose rank is more real. There's a lot of "my teacher/system is better than yours, etc.
Rank is part of the practice...even if there is no formal rank system. Others will always set up a "pecking order" of some sort.
Such is life. It's human nature. There is a lot of emotional baggage connected with rank. I believe that is precisely why we need it! It is a koan (Zen puzzle) which we need to work with. It's a conundrum which we all need to wrestle with and come to a place of balance.
Do your practice. Keep experiencing, learning, and practicing for the sake of the practice. It's easy...just care and not care at the same time!
Struggle with it until you don't...