It's primarily helpful to jQuery itself. The problem is that most libraries have blindly assumed that specific browser bugs (such as an Internet Explorer bug) w

It's primarily helpful to jQuery itself. The problem is that most libraries have blindly assumed that specific browser bugs (such as an Internet Explorer bug) will exist forever in all versions of the browser. When the time comes for IE to fix the bug (and it will come) the library will break due to the blind assumption. Using feature detection, like we have, is a sure-fire way to make sure that this doesn't happen. jQuery.support, itself, will likely only be marginally useful to those outside of jQuery core (since we're checking for some very specific bugs or features). That being said we have documented it since it could still be useful.