I've recently become acquainted with the work of Tommaso Tesei, Gabriel Said Reynolds, Andreas Kalpony and Nicolai Sinai, who from my non-specialist perspective appear to be credible scholars in Qur'anic studies. These authors have recently made arguments for a model of multiple authorship for the Qur'an, either as a redaction of pre-canonical written texts from different authors (as postulated by Reynolds) or as containing a core that goes back to the historical Muhammad, that was later expanded by people in a different sociohistorical context after his death (although Sinai appears to believe the Qur'an is still primarily the work of one author, whereas Tesei is much more skeptical). This is in contrast to what many of these scholars note has been the prevailing scholarly consensus, namely that the Qur'an has a single author.

What has the scholarly reaction to these arguments been? What have the recent counterarguments, questions, and rebuttals from experts been about the issue?