All the damn time.
I think this question can be considered in two different ways. Firstly, just at face value: I do the typical talking to myself. The arguments in the showers (that I always win), the walking myself through a process (this goes here and that’s what I do next), and the mumbling to myself whenever some horrible memory rears its head and I just want to sink into the ground never to be seen again.
You probably do something similar (and if you don’t, what is your secret?)
Secondly, I could read this as a writer would, because let’s face it, us writers are ALWAYS talking to ourselves.
Our characters are literally just figments of our imagination, dreamt up and put down on paper. So whenever those characters argue, it’s like I’m having an argument with myself. I’m literally standing on both sides of that argument, documenting the conflicted emotions from one perspective and then swapping sides to do the same for the other perspective.
It’s like Quicksilver playing ping pong with himself, running back and forth before the ball bounces.
Only each side of the table needs to have a completely different personality, a completely honest and real reason for everything they believe and every action they make. Because of this complexity, it’s not rare to read stories where the characters fall into a couple different traps.
One, the characters will all tend to believe incredibly similar things, leading to very little inter-personal conflict and too much this-is-what-the-author-believes seeping up around the edges of every page. This is when you might have trouble differentiating characters because they’re not distinct enough.
Two, the author chooses a side. This one is also pretty common and happens a lot with antagonistic characters even if the protagonistic characters in a story are done well. [This is where the villain is one-dimensional with their only defining characteristic being “evil” or something of that nature.]
When this happens in the arguments between protagonists, it becomes less apparent, but no less frustrating. This is because the “author’s side” will have clear, concise, intelligent arguments. The “author’s side” will come off kind or empathetic. The “author’s side” may even come off preachy. Ultimately, the “author’s side” of the argument will win because they’re not really engaged in an argument.
They’re not really engaged in an argument because the “losing side” is only there to show how intelligent the “author’s side” is. The “losing side” of the argument will state pitiful or false approximations of an argument that can easily be shuffled aside by a crappily-crafted rebuttal from the “author’s side.”
Basically, this is the argument in the shower we all do, only these authors are stamping those shower arguments down on paper instead of keeping those one-sided, self-aggrandizing wish-fulfillments in the shower where they belong.
So, in short, yes, I talk to myself. I talk to myself out loud and on paper (and the computer). I try my hand at imagining complicated emotions and thoughts, even those I don’t agree with, so that the characters I craft might come off real and dimensional even when, in reality, they’re just figments of my imagination.
And hopefully yours too :)