Issue summaries are out of date most often and do not reflect new comments, arguments, and details.
Contributors need to read all comments to determine which details they are missing.
Goal
Visualize which comments were wrote before the last issue summary edit.
Details
The last edit of an issue summary "should" reasonably have incorporated all comments to that date. That's a pretty hefty assumption, but a logical one, and should hopefully work out for most cases.
The issue summary authoring information is not exposed on an issue, as it's bogus.