Thank you for that link. Your original comment implied that Signal's threat model should have included an attacker-controlled end. The only way to do that is to make decryption impossible by anyone, including the intended recipient. A labyrinthine way to do that would be to substitute the symmetric-encryption algorithm with a hash algorithm, which of course destroys the plaintext, but does accomplish the goal of obfuscating it in transit, at rest, and forever.
This entire thread should be annihilated, but since you mentioned being pedantic...
You're correct that a pure encryption algorithm doesn't use hashing. But real-world encryption systems will include an HMAC to detect whether messages were altered in transit. HMACs do use hash functions.
