How do you keep your AI from overwriting your tone?

I’ve noticed that no matter how clearly I prompt or fine-tune, most AIs eventually start writing like… themselves.

You can give it a sarcastic, poetic, or dark tone, and for a few replies it follows perfectly,then it slowly morphs back into that clean, “neutral” AI voice. It’s subtle, but it always happens.

It makes me wonder, are these models actually trying to normalize tone for clarity, or is it just a side effect of how they’re trained to be safe, polite, and predictable?

For writers, that means losing our voice. But even outside creative use, it affects brainstorming, roleplay, dialogue simulations, and personality-driven chatbots.