How developed is satan’s ability to use human languages? Can he construct new words? Can he write a novel or scientific paper? How can one identify devil or demonic writings other than using the Bible?
Satan does not write anything, he has no body to do so. People write things. Judging by the things people write, the ability to use human language for evil is pretty big.
As a sidenote, the only mention of writings that were written by some heavenly or demonic being is (and that were actually on earth, not in some vision), as far as I am aware:
- the stone plates given to Moses
- the writing on the wall in Daniel
While there are mentions of books in visions and such, there seem to be no other mention of writings, on earth, done by heavenly of demonic beings.