Diff two files without SourceDiff.
On the RHS, type a few characters and hit ENTER.
(See previous bug report)
On the LHS select another line - without changes, and type a few characters.
Note that what you type is highlighted as a difference.
Now, do the same on the right --- what you type on the right is NOT highlighted.
Make a change to the same line on the left and suddenly the right side is updated correctly.
