[firepacket]

I would think the courts would recognize a difference between advertising to the end user for the purpose of purchase/consumption, and advertising to 3rd parties as part of a compatibility protocol.

The UA string is not visible to the consumer, and wouldn't affect the number of people who download and install the browser.

Its only purpose is to ensure compatibility with the server after the browser has already been installed.

Also I wouldn't say the browser is actually impersonating another browser. If it was trying to impersonate, the UA string would need to match the other browser exactly and it doesn't attempt to do that. The string is still uniquely identifiable as an IE11 UA.