The aim of this PEP is to standardize the high-level structure of docstrings: what they should contain, and how to say it (without touching on any markup syntax within docstrings).
The PEP contains conventions, not laws or syntax.
"A universal convention supplies all of maintainability, clarity, consistency, and a foundation for good programming habits too. What it doesn't do is insist that you follow it against your will. That's Python !" —Tim Peters on comp.lang.python, 2001-06-16
If you violate these conventions, the worst you’ll get is some dirty looks.