You just press the :) button on the menu that's on top of the comment box thingy.
And then you can use any of these smilies:
Kappa:zombie::yuck::yawn::wtf::writer::woot::wideyed::watching::wacky::vulcan::vomit::vamp::turtle::troll::stop::stinkyfeet::spitoutdummy::spam::sour::sorry::snaphappy::smuggrin::smug::singing::shy::shifty::shame::rage::punch::pompous::playful::pigeon::pics::phantom::penguin::peeking::panda::oldman::nurse::nailbiting::muted::mooning::meh::mask::lurking::lock::link::kiss::joyful::jimlad::jawdrop::inpain::hurting::hungry::hungover::hilarious::headphone::happy::grumpy::greyalien::greedy::facepalm::eggface::dummy1::dummy::drowning::droid::doctor::depressed::dead::cyclops::cow::couchpotato::coldfeet::cold::clown::cigar::chicken::cat::bucktooth::brb::borg::bored::bookworm::blackeye::blackalien::bigtears::beaver::bear::banghead::bag::astronaut::artist::arghh::angelic::android:evilfuzzlrfuzzlro_O:rolleyes::oops::eek::D:p:cool::confused::(;):)
