'Echo chamber' is an odd thing to say. X has many center left and hard left accounts, they're not banned in the same "women can't be men" was during Woke 1.0.
Elon Musk declares ‘cis’ and ‘cisgender’ will be considered slurs on Twitter that can be punishable with suspension
https://fortune.com/2023/06/21/elon-musk-declares-cis-cisgen...
There are tons and tons of people using the term. All the time. Last result was 11 seconds ago (as of posting this).
Slurs aren't allowed on most platforms.