It's not good for any entity to role play without signaling that they are role-playing. If your premise is wrong, would you rather be corrected, or have the person you're talking to always play along? Humans have a lot of non-verbal cues to convey that you shouldn't take what they are saying at face value - those who deadpan are known as compulsive liars. Just below in them in awfulness are people who don't admit to having being wrong ("Haha, I was just joking" /"Just kidding!"). The LLM you describe falls somewhere in between, but worse if it never communicates when it's "serious" and when it's not, and bot even bothering with expressing retroactive facetiousness.