Scholarly Kitchen has a post on copy editing and open-access repositories.
We should remind ourselves that all three studies investigate the changes that take place after a manuscript has passed through peer review. The purpose of copy editing is not to detect serious flaws in theory, methodology, analysis or interpretation — that is the responsibility of peer review — but simply to make a paper more consistent and readable. We should therefore not expect to find fatal errors at the copy editing stage, as implied in the Goodman study.
Still, we are left hanging on whether copy editing sufficiently improves an academic article to justify its persistence, and ultimately this question rests on whether you value its services.
I think that the Thatcher study (with which the author began the article) had something interesting to say about Harvard open-access documents:
[M]ost errors were minor, such as spelling errors, subject/verb disagreements, dangling modifiers, and others Thatcher calls “stylistic infelicities.†His editors also spotted more important problems in the author manuscript, such as quotation errors, citation errors, and errors in tables and figures. One editor came up with a more disconcerting error in an author version: The omission of author identity details, conflict of interest statement, funding information, and an acknowledgment section.
Interesting. Harvard. One of the leading universities in the world. But still there were problems.
Would this indicate to us a need for peer review? Would it indicate the same to our students?