One improvement coming with the next unstable release 1.3.7 is a bit more intuitive proxy configuration. So here is like it currently (1.2.x) looks:
and here is the new interface:
While the changes do seem cosmetical at first the rewrite also solved some problems in the code behind it. So until now Liferea just reused the GNOME proxy gconf keys as it's own. Thereby you could mess up other GNOME programs from within Liferea. Also due to the limited options until now you couldn't use the environment $http_proxy variable to overrule manual settings. There was also no way to enforce no proxy when $http_proxy was set. These configuration variants are now covered by the improved dialog.
And finally: no explanation text anymore about the handling of the GNOME proxy preferences.