Reddit thread: https://www.reddit.com/r/linux/comments/5yvntm/former_head_of_microsoft_office_development_brags/
The final decision to build the "Word Web App" rather than "a new web-based word processor from Microsoft that is not fully compatible with Word" (and similarly for Excel, PowerPoint and OneNote) was strongly driven by the belief that the file formats continued to serve as a critical competitive moat with immensely strong network effects. In fact, an argument can be made that the Office file formats represent one of the most significant network-based moats in business history (with Win32 and the iOS APIs as two others). Even applications like OpenOffice that were specifically designed to be clones have struggled with compatibility for decades. By embracing that complexity, and the costs, we would deliver something that we knew was fundamentally hard to match, especially if there was any confusion or hesitancy about the commitment required to compete.
I've said before that even Microsoft couldn't re-implement MS Office file formats in another product with perfect compatibility, and here they admit it!
Yet in 2004, another Office dev-manager talks about how precisely reverse-engineering WordPerfect's file format gave Microsoft an advantage in converting WordPerfect users to Microsoft's products:
Other moves were tactical. The Word planning team discovered that the WordPerfect sales force was going around to customers and showing Word opening a complex WordPerfect file (printer.tst) to show how bad the conversion was, and therefore how pointless it would be to try to switch to Word. So the Word team organized a special dev team that focused entirely on WordPerfect document import, "reverse-engineering" the WordPerfect file format (documentation for which was jealously guarded, as was the norm back then). Their goal was to make any WordPerfect doc open flawlessly in Word, but in particular their goal was to have no errors at all on printer.tst. Later the Word sales force used that same file when talking to customers as proof that Word 6.0 could open WordPerfect files flawlessly.
Original document: https://hackernoon.com/complexity-and-strategy-325cd7f59a92
Meanwhile, Valve keeps hiring talented (this time a veteran) developers to improve the Linux graphics stack: