As a new answerer on StackOverflow, I found the Edit Summary field misleading. A commenter asked for an update to my answer, so I updated the answer, and explained the update in the Edit Summary, assuming it would show up below my answer, but it doesn't show up anywhere on the page. So I had to update my answer again, including the summary of the edits in the answer itself.
If it's only meant for explaining spelling, grammar, and formatting type updates, it could be made more explicit.