Ana searched for rules about punctuating deep POV and found more useful advice.
In my go-to book on editing (Self-Editing for Fiction Writers), Browne and King have a chapter called Interior Monologue. They write:
"So what's the right amount of interior monologue? Sorry, you're on your own with that one. The balance you hit depends on what your characters are feeling, how important their feelings are to the story at that point, how you want the scene to flow, and, especially, how evident their feelings are in other ways.
"How do you handle your mechanics so that the interior monologue reads smoothly and professionally? As with dialogue mechanics, the sterling value is unobtrusiveness. And there is one actual rule.
"Never, ever use quotes with your interior monologue. It is not merely poor style; it is, by today's standards, ungrammatical. Thoughts are thought, not spoken.
"Also, it's rarely a good idea to have your characters mumble to themselves or speak under their breath. It's almost always going to come off as a contrivance.
"And whether or not you are writing with narrative distance, it's not a good idea to cast all of your interior monologues in italics. Since long passages in italics (or, indeed, any unusual typeface) are a pain to read, you can only use this technique effectively for passages no longer than a short sentence or two. Even this brief passage is too long, don't you think?
"...frequent italics have come to signal weak writing. So you should never resort to them unless they are the only practical choice for self-conscious internal dialogue or the occasional emphasis.?