Their replies are only obtuse because you fail to see that you’re being made fun of for having such a ridiculous pedantic position about this. “Terminal” does not mean shell when you read the Telnet RFC. It means TTY. A human to machine interface. MUDs implement the Telnet protocol and provide a remote TTY. What’s running on the terminal is absolutely irrelevant.
> Your MUD wizards made a bad, bad choice long ago when they picked port 23.
I'm confused. I refer you to my previous answer. Which does not specify a port, nor does it need to.