Orthogonality for orthogonality's sake is not something I'm keen on.
An initial underscore already conveys strong feelings of magicalness to a C programmer.
We all agree on the necessity of compromise. We just can't agree on when it's necessary to compromise.
What about writing it first and rationalizing it afterwards?
That which hits the fan tends to get flung in all directions.
It's there as a sop to former Ada programmers.