Too many long-winded replies to read.
My answer is pretty straightforward: whatever I, the player, decide the character is going to do, is what is IC for the character.
Source: MY REAL LIFE FUCKING EXPERIENCE.
I am a fully fleshed out real life person who makes real life decisions on a daily basis and those decisions do not, under any criteria ever posited by any roleplayer (or critic of television or literature), follow any sort of consistency.
Yesterday, I had trouble texting the girl I like. Today, I am texting three. My mood, the amount of sun in the sky, your mom's underwear choice half-way around the world, and how much coffee my work budy has had before 10 am might OR MIGHT NOT subtly change what I decide.
We pigeonhole characters into "is this IC or OOC for them" because we're mostly uncomfortable realizing that people vary A LOT MORE THAN CHARACTERS DO, because characters are constructs that we define and limit to show them to people in identifiable ways.
I have had characters who were terminal horn dogs just... turn down sex. For no reason. "But Devlin ALWAYS WANTS TO FUCK, what's wrong, Coin? Are you okay? Is Devlin okay? THIS IS SO OOC."
No, it's not OOC. He just doesn't want to fuck. Sometimes Devlin doesn't want to. Sometimes he does. The latter is more common.
Now, NARRATIVELY speaking, when we're talking about television and literature and movies and what not, yes, consistency of action is important because it keeps the story flowing (though I still absolutely roll my eyes whenever people go 'that character would never doooooo thaaaat' MAN STFU, PEOPLE ACT CRAZY ALL THE FUCKING TIME), but while roleplaying?
Fuggedaboutit.
Also, this extends even further. "Coin, why did your character do that, it's going to lead to a bad place!" "It's what he would do." <--- perfectly reasonable response, EVEN when taking the above into account.
'Cuz I am my character's puppetmaster. I decide what he does.
Usually it's consistent. But sometimes it's not. Deeeeeal with it.
Bring on the complaints. I haven't heard many on this directed at me, though, sooooooo...
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This post ended up way more aggressive than intended, but I'm totally committed now, so fuck all of you.