The title of the text (between the "matches" and "custom filters" bubbles and the actual text view column) unnecessary large to me. font size smaller a few notches would totally do it and save a bit of screen estate
The underlining behavior when moving the mouse over the colored segments of the text-view left column is not good. The reason for this is that these colored segments do not correspond to any meaningful entities, and underlining them creates the wrong impression that these could correspond to "matches" which isn't the case. I'd suggest just to remove the underlining behavior, the rest is fine.
As we discussed previously, when mouse-over a match in the middle view, all segments in the left column that contain that match in their 'matches' property should be highlighted with gray background as well.
The current state (Nov 20) is much better already!
A few points still remain:
the underlining of the clicked segment is not necessary and might be more confusing than helping. Similar the grey background which might just slightly conflict with the blac
the black higlighting is great and works very well. The only remaining problem is that the highlighting disappears when moving out of the middle view, which can be an obstacle when the user wants to scroll through a longer match on the left column of the text view.