Comment by smarx007

I had moderate success using https://www.iso.org/ISO-house-style.html converted to markdown and narrowed to the guidelines starting with "Plain English" and ending before "Conformity and conformity-related terms" (plus a few other rules up to and including "Dates"). A quick estimate puts the whole Markdown document at 9869 tokens - quite manageable. I generally prefer the style of the Microsoft Writing Style Guide but ISO house style is the only one that fits nicely into a prompt.

Looking forward to your model/product!

P.S. https://www.gov.uk/guidance/style-guide/technical-content-a-... also looks useful