actually there is a sneaky workaround that can be done because your chats are being logged.
you can use public key encryption using ECDH for your key agreement protocol and you can use the game client to send public keys to both parties then derive the shared session aes key that will use to encrypt chat. so other then sending the key agreement protocol then using aes256 encrypted plaintext no one can read your text in game and its actually secure. this method can actually be deployed anywhere. the example here is in gcm mode:
here is key 1 shared: BABLW667mtdxc+X7X+Om2txFrRfXMkBUupa/Y0QyqKyfCGjvce/PH+L4OTeRLkSE0cTlDe/QGomEuuiflbKBAChcUAFxNxmpvi3Gydn5Vv60mnU7eqQHI/aPNFMW3hhyDheK3j7BaXStY38y7g8oIe90O+o5I7SipF9yQqZ4HLV7TbwF8w==
here is key 2 shared: BAGFF4/uG6hUr9d6GpS4UquazbfErypRVHXAN0cZlVuxB3I90qWgq/solZCvR1qvLUb2ID1A9SyVAZ5GJagRmFxijwAjoMVZfES3g3UWZmg0g+jL2BAYjMkYHksRsWhOaoPt+E8tlfxouADNphFkHxjCX0xbs6W1aOKZ9LwtYI1LJLTJGA==
next we will derive the aes key: 91527769ccea81e8bf0e33058ecac6d8e4b238c433a98aa46a1c6f7eab314a0accbb63f7c23445c3f32e8498165cae9a2141b1ebcfa8a31bd5ec0ede882e8673 // this derived key is not pasted in game or the traffic can be decrypted. you can have forward secrecy if you only use the key once then rekey after 100 messages.
now here is secure encrypted chat: U2FsdGVkX19Xo4v3wQfH3l6YDn5HMgdZ2WBaZ5o9l2RudXnZa3ufZ8w9zmQ3s875bn2vnCZXjfUzIqCMLDqgu7BplKDsy4zrdSFwdFNw
decrypts to: you wont be able to read this so dont even try
now in diablo the traffic is tcp and this uses no encryption so you can sniff the traffic and just copy the key outside of the diablo 2 window. then all you would need to do is paste your key in the diablo 2 window and the other guy would sniff traffic and grab that key. you paste 1 key (your pub key) and basically you got encrypted traffic within d2. it sounds complex but its simple because no encryption on the network traffic. i dont know if d2r uses tls or tcp i dont have it installed. but this method for diablo 2 at least is completely patch proof and works outside of the game client. you can paste keys inside the d2 window using c++ with windows api or lua with winapi installed. i made a tool that does just this but its not made for d2 yet.
ok thats a lot and i know most are not good with reading
but the purpose of this is your chat wont ever be subject to account suspension because no one can read it except for those with the correct key agreement. also the key agreement is really fast (its ecdh is way faster then rsa) and yes its very very secure.