Charliehall and Sam2,
No one denies that when people are talking in the Torah it is the person’s words and not Hashem’s words. That isn’t apikorsus. It is apikorsus to say that Hashem did not authorize those words to be put into the Torah but Moshe (or some hypothetical anonymous author) decided to put the words in on his own accord.
All the Ibn Ezra is saying is that Moshe is restating and paraphrasing the 10 Commandments, not quoting them. That is the opposite of what Farber is saying. Farber is saying (at a most charitable reading) that the differences between Shemos and Devarim are that there are two different traditions as to what Hashem’s words were but both hypothetical authors think they are quoting Hashem.
I disagree that the Ibn Ezra said things that were apikorsus according to the Rambam (which is the normal standard used today).