GPT-5.1: A smarter, more conversational ChatGPT | OpenAI

This additional level of personalization for ChatGPT seems like a notable add:

Earlier this year, we added preset options to tailor the tone of how ChatGPT responds. Today, we're refining those options to better reflect the most common ways people use ChatGPT. Default, Friendly (formerly Listener), and Efficient (formerly Robot) remain (with updates), and we're adding Professional, Candid, and Quirky. These options are designed to align with what we've learned about how people naturally steer the model, making it quick and intuitive to choose a personality that feels uniquely right.

I would think they would be able to make a guess at the best tone to respond with based on how you talk to ChatGPT with your questions.

I've found success telling ChatGPT what your Insights Discovery profile is and letting it use that in how it works with you. It adapts very well based on that information.