This is a great idea! I tried it on a 200-page document [1], and it took over a minute to process in my browser, and the result seems to be about 75% highlighted. Not sure if it's the "math-ese" or length that is the issue.
One cool thing is that it highlighted both the same sentences in English and French. I presume you translate the text before analyzing.
[1] https://www.math.mcgill.ca/darmon/theses/leahy/thesis.pdf