Your votes helped get this fixed. I've reported three more bugs with word wrap on the new developer community website. If you can reproduce them, please vote for them there.
1. Triple click should select logical line https://developercommunity.visualstudio.com/content/problem/138283/triple-click-should-select-logical-line.html
2. Pressing End key twice should move cursor to end of logical line https://developercommunity.visualstudio.com/content/problem/138274/pressing-end-key-twice-should-move-cursor-to-end-o.html
3. Cut command should delete logical line https://developercommunity.visualstudio.com/content/problem/138259/cut-command-should-delete-logical-line.html
This appears to be fixed in Visual Studio 2013! Thanks (at last)!
If you think "this isn't worth fixing because only a few Visual Studio users use word wrap", consider that "most Visual Studio users don't use word wrap BECAUSE IT'S BROKEN".
You can run .csx scripts with C# Interactive (csi.exe). It would be neat if you could debug them in Visual Studio.