The most likely failure of data integrity on Hive is the same as it is on Steem: 17 consensus witnesses can censor anything they want.
Otherwise, generally, failure happens. It's just unrealistic to claim something is failure proof, and generates skepticism. Better language would simply state that data integrity is a primary purpose of the blockchain, and every effort has been, and will be, undertaken to maintain data integrity.
People know things can fail, and trying to claim something cannot fail, or even implying it, sounds disingenuous. It's much better to not leave readers feeling even the least bit skeptical of claims in the white paper, even if the language isn't the most powerful promotion of Hive that could be phrased. The most important sense readers should have is of the integrity with which Hive is discussed. That creates strong confidence in the audience.
The ability of the witnesses to alter the blockchain is undeniable, and it has happened on Steem, so there isn't any good reason to imply it can't happen.
Editing is difficult, for both editors and authors. I am glad to see my thoughts have been useful to you in your task.
Edit: regarding 'extraordinary', different authors write differently, and use different words. All I can do to be of assistance to you is make suggestions. This is your work, and will be in your voice. Unlimited is not the best word here IMHO, because it seems over the top, making promises Hive can't deliver.
I am glad you aren't just going to let me dictate to you, because that's not at all what I want. Use the right word for your voice, even if it's unlimited. It's a small thing to be judged by me. Your judgment is what matters.
I still have to finish up with the list of your suggestions. I stopped halfway yesterday to get the Tech Vision doc out.
How would you define "integrity"?
In this context, it would be immutability. Extant data is the same data that was originally provided the blockchain, plus new data. The old data hasn't been altered or removed.