In Dutch, teachers commonly use the phrase "spreektaal", literally translated "spoken language" to denote a turn of phrase or sentence that, in the context of the assignment, is too informal. "you would not see this in writing, but it's normal in everyday speech." Either it's too new, or someone accidentally wrote down their verbal tic, etc. You'd see this written in the margin where points are deducted from assignments for it in educational settings.
In this context, the word has a very specific meaning. I've been trying to figure out what the equivalent would be in English. If a teacher would strikethrough a bunch of "so like" constructs in an essay written with a 'valley girl' accent1, what would the short word/phrase written in the margin be?
This is a very common mistake for students to make, so the big phrase in quotes above seems 'too long' to not have some common term for it. Is it "conversational writing"? I can only find that term with positive connotations attached to it.
1: This doesn't mean that a 'character' can't speak 'like so', it's where the narrator mistakenly takes on what's usually the writer's speech patterns.