Two Forms of Developmental Editing
In my experience, there are two major forms of developmental editing: high-level with just comments, and high-level with comments and adjustments.
It’s important to know the difference between them, and which one you should be doing on a given pass & project.
High-level with just comments
You do these sort of passes when the writing is rough, often intentionally so–experimental work, early passes on a long project, that sort of thing.
When you’re doing these, it’s important to explain what problems exist and what needs to be done. Light copy edits when they catch your eye, but your efforts need to focus on communicating issues, because other work you put in will likely be rendered moot in revision. (That said, sometimes even when the work itself is rendered moot, a writer seeing those small copy edits is useful for future guidance.)
What’s really important is to not get caught up in rewrite work. If you start in on a part of the manuscript that would take much more effort to rewrite than the communicate the issue, don’t rewrite it. That’s not your job at the moment.
High-level with comments and adjustments
On the other hand, some passes come with the expectation that the editor will do a significant portion of rewriting. it’s akin to the above, except those comments you’re making about rewriting are comments you’re making to yourself.
I’ve found I like to do the just comments pass first, with thoughts on rewriting, and then go and tackle those rewrites. That avoids the perilous issue of doing rewrites as you encounter text, only to discover that later text handles what you’re doing or you’re accidentally contracting elements in your rewrites.
Of course, not everything can be easily rewritten by the editor. Some points are discussion or flags for future passes. And comments about why something was rewritten is helpful if the draft is going back to a writer or other member of the team.
A word of warning
If the developmental editing pass like this, with heavy rewrites, goes right to layout, expect the book to be fucked. The pressures of doing dev work and rewrites on top of copy work on what otherwise passes through means that you’re likely to have issues that require a copy editor to sort through. In essence, your dev editor became a writer, and that makes going right to layout akin to having a writer skip editing and go to layout.
So, you know, avoid that.
That said, if the process is writer->dev editor->writer->same dev editor, but doing copy, then you’re probably sorted out.
Doing the wrong one
The trick to this is to know what should be done, because doing the wrong one can derail a project once it gets out of the editor’s hands and people discover the miscommunication of role. Doing just comments when rewrites are expected means the schedule’s thrown off, as work that was expected to be done wasn’t. On the other hand, doing rewrites when just comments are expected means pressure on the schedule to complete a more intensive job than anticipated, with the possibility of friction when a writer was expecting comments and to do the adjusting herself.
Either way, as an editor, it sucks to find out I was doing the wrong one on a particular pass. Most of the time, I’ve done the “rewrite” when “just comments” were wanted, and I’ve stressed myself out pushing a draft forward that didn’t need as much push from me as I thought. It makes the end of that work sloppy, and when the schedule is anticipating only comments, it means pushing the schedule back.
How to do the right one
Now, it might not make sense right away to ask. After all, sometimes the answer is “I don’t know, editor. You tell me?” In those cases, read the manuscript some first. If you routinely come up to places that need extensive rewriting, that’s a good time to bring up some issues and ask what’s expected, then compare what’s expected with what you can do in the time frame that you’re given.
(And places where the rules need reworking, well, that’s a different beast entirely.)