I think of editing as a series of teachable moments - my goal is to help the writer develop the best product s/he can. I fix changes, yes, but ultimately, I hope to provide information on how to fix changes so that in revisions and in future works, the author becomes a better writer because s/he has learned. In the editing process, I try to do this in three ways: Tracked Changes to fix grammatical, mechanical, and structural issues; Comments that relay to story-related issues, and Comments that I call "readerly comments".
Tracked Changes
These are the things clients typically expect to see fixed. Any issues with grammar, mechanics, structure (commas inside quotation marks, moving taglines to middle of long dialogue passages, etc.). These are typically accepted by the client overall when s/he receives her/his edited manuscript from me.
Comments Regarding Story-Related Issues
While having a clean copy (what's done in Tracked Changes) is cool, none of that matters if the story itself is not strongly written. I use comments to talk about story-related issues, such as underdeveloped characters, holes in the plot, weak development of tension, superficial dialogue, and weak beginnings and endings to chapters and/or scenes. This is primarily where teachable moments come into play. Typically, I will stop at the point of issue and write a comment that: 1) tells the client of the issue, 2) explain why I see it as an issue, and 3) provide suggestion(s) on how to fix the issue. This is where the bulk of my time goes, especially in a first edit because like I said, if the story is weak, grammar and mechanics are the least of a client's problems.
Readerly Comments
As I edit, I attempt to be "the average reader" of a client's book. And just like when readers wants to yell at a character, toss a book because it's irritating them, laugh out loud because something is so funny, or sob because they are touched, I like to illustrate those moments in the editing/reading of a book. In the past, I see these at times as comic relief for the client. Many of them contact me, laughing, because those comments were so funny. However, they do serve another purpose. If I'm laughing in a spot that's not intended to be funny, that relays something to the client and makes her/him have to consider what to do about it. If I loathe a character to the point of not wanting to read the book and the client actually wants you to like the character, then the client needs to consider what changes might need to be made. So, in the end, while the comments I make tend to be funny (because they are so off the cuff), they can be instructive, too.