Note that you don't have to save in *.doc format. Setting compatibility to Word 2010 will suffice. However, doing so requires a trick.
Here's how to do it: Make sure the document that you want to change is the active document in Word. Press Alt+F11 to display the Visual Basic Editor. Press Ctrl+G to activate the Immediate window. Type
ActiveDocument.SetCompatibilityMode wdWord2010
and press Enter. Close the Visual Basic Editor and click File | Options. In the Advanced category, scroll down to the bottom where you will now see the list of layout/compatibility options. For "Lay out this document as if created in," select Word 2010.
Click OK to close the dialog box and then save the document.
Everything, including text boundaries, will work the way it did in Word 2010.