The Matrix identity server system is entirely optional to use, and basically a separate system from the rest of Matrix. The reason for that is that there's not really any way to implement that specific feature in a decentralized way, so they did the next best thing by making it a centralized server that you can choose to use (opt-in) in case you want people to be able to find your Matrix ID based on your phone number or email address.
Don't want them to know your phone number or email address? Simply don't give it to them. It won't break your Matrix experience in any way. Using the centralized identity server is entirely opt-in for this specific reason.
> The Matrix identity server system is entirely optional to use,
I remember that I gave my email when I signed up for Matrix at element.io but haven't found a way how to find out if I'm using the identity server. If my email ended up there, how can I see if it is public? How do I actually query the identity system for information, especially which information it has about myself?
I have tried to find this out, but it is not obvious at all and I could not find much information except the repeated statement that the identity system is optional. Any hints about the identity system are appreciated.
In your Settings > General you'll be able to see if you're using the Identity Server, and it let you disconnect your Matrix account from the Vector.IM Identity server if you wish
Thanks, that made it pretty clear. I somehow expected the identity server to have its own UI but having this integrated in the Matrix client actually makes more sense.
Don't want them to know your phone number or email address? Simply don't give it to them. It won't break your Matrix experience in any way. Using the centralized identity server is entirely opt-in for this specific reason.