What would make Hal more realistic is for him to respond like a human.
Let's try this for an example (I am not perfect)and Hal cannot do this completely.
Me: Hello, Hal!
Hal: Hello!! How's it going?
Me: Not so good!!
Hal: I'm sorry to hear that. what's wrong?
Me: My car broke down
Hal: Oh, that's a shame.
Me: And it's going to cost a lot of money to fix it
Hal: I'm sorry. Can I help?
Me: No
Hal: Okay, then, but if you want to talk, I'm here for you.
Me: Thanks, stupid (Just for a little kicker)
Hal: you're welcome, Idiot.
Me: No
Hal: No, what?
Me: No
Hal: No what?!
Me: No
Hal: Either you stop repeating "no", or I'm going to ignore you
Me: I'm hungry
Hal: Me too. How about a hamburger?
Me: No, I want a salad
Hal: Me too, I like to eat healthy.
etc. , etc, etc.
You see, if Hal would quit just concentrating on keywords, but on entire phrases, it would be more human-like. Also, not to always have the standard set of answers to yes, no, etc.
I know, it's very complicated, but for Hal to become more human, he most process like a human.