Re: Why aren't paragraph-s\(tart\|eparate\) buffer local by default?

[Richard Stallman]

    Why aren't paragraph-s\(tart\|eparate\) buffer local?  There doesn't seem
    to be any call for having global values for them since so many major
    modes (amongst them C Mode, Lisp mode, Texinfo mode) give these variables
    mode specific values.

There is certainly a reason for these variables to have global defaults.
The paragraph commands can be used even in Fundamental mode.

We could consider making them automatically local whenever set;
that doesn't require eliminating the global defaults.  I am not
sure this is bad, but it isn't obvious to me it is desirable.

I think the right fix for the problem you encountered is to make
c-set-style check that the buffer has an appropriate mode before it
does anything else.