Yes, it's an interesting problem (for which, as you can see above) I was drafted. It's a lot harder to identify a sentence than it might seem.
Your macro is an admirable attack on the problem. It also illustrates just how hard it is to use actions to deal with a complex situation in Keyboard Maestro's visual programming language. You can get tied up in knots pretty easily, scrolling around to find out where you are (I'm in the middle of just such a project right now, in fact).