Beside looking and sounding clunky when you read it, but I have to wonder, "is the 'of'' necessary?"
Take this sentence as an example "Julie got up off of the sofa and headed for the kitchen." It is clear Julie was sitting down and got up, and she then walked to the kitchen, right? I don't know about you but I stumble as I read the words 'up off of'' before the rest of the sentence rolls smoothly again.
Well, what if we reduce the word count by one little word and just wrote "Julie got up off the sofa and headed for the kitchen." I think it is still clear Julie was sitting down and got up, and then walked to the kitchen. But this time, I didn't stumble while reading the passage. And as a reader, that is what counts when I am determining if the book is fantastic, good, okay, so so, or not my cup of tea.
Now, I have just spent the last ten years trying to improve my novel writing skills; but, although I have improved greatly in the area of grammar (I was always a good speller, and fairly adequate punctuation-er) I still have a lot to learn when it comes to understanding grammar at the highest level. Maybe the 'up off of' is grammatically correct and thus dropping the 'of' isn't, but as a reader, I would rather read a sentence that I can read with ease instead of one I find myself tripping over.
Maybe (which I suspect is more the case than not) it is a difference between the Australian conventions I have learned, and that of other countries. Either way, I have to say I would avoid the unnecessary word of 'of' because it doesn't change the meaning of the sentence in any way by excluding it, so make the jump and start excluding it and see if your sentence sounds stronger and better for it.
Do you use 'off of'? Are you an editor that can explain whether it is grammatically correct or incorrect to include or dump the word 'of'? Please comment below!