That's a false dichotomy. If you launder rambling pointless prose through the llm you don't trade the personality of the writing for a well reasoned argument with clear points, you just lost the personality and gained shitty writing. LLMs aren't magic and can't make your point for you if you don't have one to begin with in the prompt. Garbage in garbage out.

I disagree. An editor can definitely make a piece of writing clearer without further input from the author. I often use an LLM to do that.

Of course, I didn't mean to imply that there's a dichotomy between personality and clarity. There's a dichotomy between ordinary LLM writing and personality.