I have an idea: If URL shortners and mirrors do not work, how about enciphering the address in some easy cypher like ROT-13 (explicitly pointing out to that fact and giving a website of which there a dozens to decipher quickly). That’s a common practice to hide emails posted in public from web crawlers, to avoid receiving spam. This only protects from automatic removals and doesn’t hide it from anticommunists however, it still being possible to be censored if someone reports it. One may have to change the cipher if some platforms start remembering the enciphered address.