The attorney-client privilege can protect lawyers' input into draft documents created by the lawyer or by the client – which of course evaporates when the client approves the finished document for disclosure outside the relationship. Not surprisingly, courts examine such lawyers' revisions to assess whether those lawyers were providing legal input rather than business, grammatical, stylistic suggestions, etc.
In Shenwick v. Twitter, Inc., the court noted that defendants withheld "several drafts of documents with comments provided with the redlined version." Case No. 16-cv-05314-JST (SK), 2018 U.S. Dist. LEXIS 185714, at *7 (N.D. Cal. Oct. 30, 2018). But because the court could not "determine the identity of the author of comments [in] these draft documents," it ordered defendants "to provide the Court with the identity of the individuals who provided the comments and link them to the comments in the draft documents submitted to the Court.'" Id.
The lesson from such decisions is self-evident. Lawyers should always memorialize their role in any drafting process, and stand ready to identify their suggested changes – including the nature of their legally-driven revisions.