Consecutive changes by the same author and kind (addition/deletion) but from different revisions are not immediately visible to the user. It would be nice to draw subtle borders for each change so that the user can distinguish them better (instead of hovering over characters and reading the tool tips).
To implement this feature in LTC Editor, I suggest the following approach:
1) Draw subtle lines "|" in the background of the text area.
2) Make sure to react appropriately to resizing and editing events to update the drawing.
See:
http://stackoverflow.com/questions/8716571/java-transparent-textarea-draw-background
Another approach would be to hook into the rendering of StyledDocument to draw the lines as part of the text glyphs.