I think an analogy everybody would understand is to think of a regular web app. If you need to add Internet Explorer support to a website that only supports Chr

I think an analogy everybody would understand is to think of a regular web app. If you need to add Internet Explorer support to a website that only supports Chrome, does it make sense to fork the website? Almost never. You just inline hardcoded elements and style stuff that only IE browsers understand masquerading as html comments so that other browsers will ignore it. At most, maybe you run/serve a platform specific piece of js/css/html. Maintaining hundreds of lines of duplicate code can become a logistical mess. Most extensions will see 95-100% shared code between platforms.