Closest they're gonna get to self-destructing messages on a blockchain is trusting the recipient to delete the decryption key after a certain amount of time, al

Closest they're gonna get to self-destructing messages on a blockchain is trusting the recipient to delete the decryption key after a certain amount of time, along with pruning expired messages from the chain (not perfect, probably good enough). To their merit, blockchain based messaging is an easy way to prevent a great deal of traffic analysis.