Well, as I said, these determinations are up to the house style.
I prefer that blocks of code hold together -- think of them as paragraphs. Spacing each sentence of a paragraph out is similarly confusing. But as you say, YMMV.
I find
return is_valid(result) ? result : ERR_CODE;
common and clear, but perhaps you don't.
I do think that any style guide should forbid while and do..while simply because for has become by far the looping construct of choice in C.
In all cases the point should be correctness and clarity, not showing off that you use unusual language features.