Re: [whatwg/xhr] Web compat implications of making getAllResponseHeaders lowercase (#146)

> which will make my response look like this:

Maybe it will, or maybe it won't.  Since HTTP header names are case-insensitive, a proxy would be totally within its rights to change the casing.  So while the response looks like that when it leaves the server, it may not look like that when it reaches the client.  Neither the server nor the client have control over that.

> it's a bug in the application when i'm doing a case sensitive comparison

Yes.  It happens to work in some cases, but is not guaranteed to work, given the semantics of HTTP.

None of which detracts from the point that changing XHR may still be problematic, or that breaking code that was already broken in _some_ cases in a larger set of cases might be a problem.  But we should all be clear that code that was not doing case-insensitive header comparisons was already broken in various cases.

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