I understand your purist position, and your Haiku example actually makes a lot of sense to me. If the choice of every word, syllable and pause is part of the creative work, then having AI recast the language inevitably changes something.

My own experience has nevertheless made me look at this from another angle. I have met people who, for very different reasons, had difficulties expressing their thoughts in writing. Some of them started using AI as a kind of bridge between what they were thinking and what they were able to put into words. In some cases, this even allowed them to participate in conversations and communities again in a way that had previously become difficult for them.

I wouldn't call the resulting text purely human creative work either. But I also wouldn't say that AI had taken their character away. In a strange way, it sometimes seemed to make that character visible again.

Perhaps there is a difference between AI replacing someone's expression and AI enabling someone to express themselves at all.

And that makes the question of character a little more complicated for me. If the thoughts, experiences, opinions, humour and decisions about what to say still come from the person, but AI helps them cross the gap between thought and language, where exactly does the person's character end and the tool begin?

I'm not sure there is a simple answer to that. But I think it's an important part of the AI discussion that is easy to overlook.