Avoiding that thread because of spoilers, but wanted to add:
The IC influences the Storymind first and foremost. What conflict does YOUR perspective create? Sometimes that’s direct (Ben Kenobi first Star Wars), sometimes that’s indirect (the cop in Die Hard).
So the answer to the question, “Does the IC impact the MC, or all the players in OS?” is neither—and both.
You just have to be super clear about the quality of that “impact.” Is it personal and YOU, or is it objective, and part of THEY? Sometimes, what looks like You is really They (particularly in Psychology Domain stories—NO SPOILERS!! 
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