Stylesheets loaded multiple times

Hi,

by inspecting commons with firebug I have discovered that somehow stylesheets are loaded multiple times. The appended picture is from a nearly vanilla commons (commons-7.x-3.17) installation, where only the themes commons_origins and at_core are installed and activated. As you can see in the picture the stylesheets are loaded twice. On my main site (commons-7.x-3.27) I have 4 themes installed and accordingly all stylesheets are loaded 4 times.

So it seems that for each theme you have installed all stylesheets from all activated themes are loaded. Is this "works as designed", a false interpretation of firebugs data or a bug???