The --mic-boost option is not (and has never been) implemented, if you look at source code it's really easy to see it:
http://mapserver.flightgear.org/git/?p= ... =next#l238About PulseAudio: FGCom doesn't care for pulseaudio driver, he uses OpenAL driver, OpenAL look at your operating system audio configuration and select the default microphone. I don't know how it works on Fedora 18 but here on Linux Mint 15 I have an "Input" drop list, then I select the device input that I want my operating system uses then FGCom (and so OpenAL) is able to use this device as input.
I would be surprised to know that Fedora 18 has a bug about audio system :/ Maybe you should ask on a dedicated Fedora forum.
I have multiple reports saying FGCom works as expected on Windows XP, Windows 8, Windows 7, Linux Gentoo, Linux Ubuntu, Linux Mint
Keep in mind that the important thing is to tell to your operating system which device you want to be the default input device. Once you are able to tell that to your operating system it should work as expected.
Regards,
Clément