Since now Portage can generate zlib-compressed log files, it would be nice for both time and bandwidth space for those to be attached as-is... unfortunately this means they are not viewable inline even if the browser supported the deflate/gzip encoding (Firefox, Chromium). If you could look into providing inline access to those it'd be fantastic :)
Even if portage doesn't compress its logs on creation, this still would be useful as it would allow larger build logs to be attached, which typically compress very well.
Created attachment 548298 [details] lipsum.txt.gz (test case)
I recall seeing such behavior at some point. Not sure if it was Bugzilla or the browser. However, one thing that's clear is that it made downloading attachment problematic.