its actually a really good request -- i will work on it.
cmpm: thanks for fielding this request initially -- i was thinking exact same thing as you, so i'm glad to read the back and forth here, helped me understand what as being asked for
Thx, i use all the time Screenshot captor specially for open source software bug "report" i use highlight with border only and no shadow because shadow add a dark effect behind the region if transparency is set.
To be honest, I mainly use Text Object as it provide exactly the same feature.
As asked by cmpm, the highlight should not change.
We could have 2 new options and ome more tool :
option 1 : "sharpen | text | cleartype like" mask in order to see text very well.
option 2 : shadow only outside object to avoid dark effect behind the complete region.
tool : round pen with diameter size.
The clipart object folder is very convenient once you know where you have to add and organize your stuff.