Все, заработал!
$(document).ready(function(){
$(".comment").mouseup(function(e){
qtext = $(this).parents("div.postbody");
if (window.getSelection)
{theSelection = window.getSelection().toString();}
else if (document.getSelection)
{theSelection = document.getSelection();}
else if (document.selection)
{theSelection = document.selection.createRange().text;}
});
$(".quote").click(function () {
uname = qtext.find(".name").text();
$('.sceditor-container')[0].value += '[quote="' + uname + '"]' + theSelection + '[/quote]'
});
});
Спасибо большое за помощь!