原来，罪魁祸首是我的防病毒软件Avast，更具体地说是集成的实时网络屏蔽。关闭它会导致响应再次在浏览器中显示为压缩。

It turned out that the culprit was my antivirus software, Avast, more specifically the integrated real-time network-shield. Turning it off causes responses to appear compressed in the browsers again.

有趣的是，Avast也在Windows 7计算机上运行，​​即使在那些计算机上响应在我的测试中适用的地方压缩。

What remains interesting is that Avast was running on the Windows 7 machines as well, even though on those machines responses where compressed where applicable during my tests.