You can offer feedback and suggestions for the 2021 edition of the Carta Fediversi in the comments section below.
If you are proposing an instance, be sure to explain why you think it belongs on the map. Is it a large instance? Does it have a special theme? What is it known for? What fantasy kingdom would it belong to? Does it perhaps have an association to a place in the real world? If the instance were a Dungeons & Dragons character, which alignment would it have? Which other instances would be nearby and why? Merely mentioning an instance isn’t enough, because I wouldn’t know where to put it.