I’m not sure exactly where 85% coverage falls. But I can say that at 75% you will have essentially zero understanding of what a text says. (Context clues don’t help you here) And at 95% coverage you will be able to understand basically the entire text.
I don’t remember the source but here is the first page of Harry Potter with only 75% coverage:
> 75% coverage
_______ ONE
THE BOY WHO _____
Mr . and Mrs . Dursley , of ______ four , ______ _____ , were _____ to say that they were _________ ______ , _____ you very much . They were the last people you ' d ______ to be ________ in anything _______ or __________ , because they just didn ' t ____ with ____ ________ .
Mr . Dursley was the ________ of a ____ called _________ , which made ______ . He was a big , _____ man with ______ any ____ , ________ he did have a very large ________ . Mrs . Dursley was ____ and ______ and had nearly _____ the _____ ______ of ____ , which came in very ______ as she _____ so much of her time _______ over ______ ______ , ______ on the _________ . The Dursleys had a small ___ called Dudley and in their _______ there was no _____ boy ________ .
Here is a similar source https://thepatrologist.com/what-98-comprehensibility-looks-l...
Those aren't random words. That's like most of the nouns and meaningful verbs. You can pluck out most of the nouns and verbs of anything and the context gets lost.
The words weren’t removed randomly. When i said “percent coverage”, I meant that the blocked words are outside of the xx percent most common by frequency.