> Building a tool to enhance the experience of another service isn't the same as building or supporting a walled garden.

Building a tool that enhances a walled garden is supporting a walled garden.

> That's like saying "developing for iOS||Android||Windows Phone||Symbian is supporting a walled garden!" or "making a petrol||diesel||electric car is supporting a walled garden!"

Where an operating system only allows you to run programs that the makers of that OS approve, then it is a walled garden, and writing software for it certainly is supporting a walled garden.

> "making a petrol||diesel||electric car is supporting a walled garden!"

Bad analogy, since none of these things are monopolies of one company.