A per-line author column would be most useful if it opens the corresponding revision when clicked, rather than showing only a name. For uncommitted changes, it could show “Working copy” instead of attributing them to the last commit. That keeps the history useful without implying the current edit came from someone else.

Showing the author beside each changed line would make review much faster, especially when a diff spans several commits. It’d be useful to include the revision or commit ID too, with the author data coming from the selected SVN, TFS, Mercurial, or Git history.