I have written a little bit about errors in editing before, but this article by my colleague Erin Brenner of Right Touch Editing says everything that I would say about the issue.
Another reason editing can’t be perfect is the simple fact that editors are as human as writers and designers and every other person on our planet. Even though we’re trained and practiced at finding errors, we do miss them. And we’ll miss more of them when there are a lot of errors in the manuscript. Catching more errors might mean taking another pass through the document, which could mean more time and more expense. A good editor keeps your timeline and budget in mind when trying to make the manuscript the best it can be.
Read the full article here.