^Good morning (afternoon? evening?) sunshine! And, incidently, I've just had a conversation about lucid dreaming at lunch today, and, saw your thread on the same matter. Been posting there.
As for the rest, yup, quite fuzzy, esp. because I, myself, have a hard time perscribing rigidly a manifestation of a behaviour on a particular function, esp. in specific case by case scenario. That's one of my criticisms of the applicability of MBTI.
Having said that, one of the biggest red flag in terms of Juno being an ISFP have been the intuition (esp. Ne) that seems to pour out of her/the character. I'm giving a few scenes as concrete examples because I just don't know how to summarize the generalized intuition that is evident in the character, so maybe the below examples will flesh it out:
There's the scene where she's walking to the abortion clinic and her protestor school friend and her converse.
Juno converses, "Cuz I knew this girl cuz she had this crazy freakout because she took too many behavior meds once, and she ripped off all her clothes, and dove into the fountain at Richdale mall and was like, BLAIGHH, I'm a cricken from the sea..." (as she does wild hand and feet gestures)
Friend: I thought that was you
Juno: Well,....um...it was good seeing you...
And, another where she's hypothesizing that the jock that hate her is truly in love with her secretly, because he likes girls who're really geeks, but, hipster geek...with glasses, and a stick, etc...etc....[the scene is a voice-over, that visualizes the type(s) of girl that jock supposedly likes, we see this random girl model being drastically changed into weird, wacky outfits, according to Juno's voiceover]
And, there's many instances of weird intuitive random thoughts sprinkled throughout Juno's dialogue and her perceptions.
Where do you see her as a sensor?