The intent is to distinguish the editing of answers from providing supportive and helpful comments. Editor and Strunk&White, IIRC, can be attained simply by editing your own posts. In addition not everyone has the rep to edit other people's answers. ...just a thought that there should be a distinction.
For example: SO question 2211388/serialize-object-to-xml-problems
I may know the answer, but there is an answer with a good start. Sure, I'll up-vote it (or at least I should). Then, instead of competing for the accepted answer, possibly duplicating most of the already up-voted answer and embellishing with some campaign style code snippets, I support the one already there.
I think this encouragement could produce higher quality answers. The downside to this, obviously, is how it could be implemented. I hope my explanation makes sense.
One possible implementation could be an icon only visible or click-able by the OP (?), or an additional option in the flag that tags the comment as supportive and collaborative.