Previews a thread's opening post, & quotes previous poster.

Duoforumhacks.user.js

// ==UserScript==
// @name         DuoForumHacks
// @namespace    http://duolingo.wikia.com/
// @version      1.0
// @description  Previews a thread's opening post, & quotes previous poster.
// @author       Dessamator
// @include      https://www.duolingo.com/*
// @grant        Public domain
// ==/UserScript==

function inject(f) { //Inject the script into the document
    var script = document.createElement('script');
    script.type = 'text/javascript';
    script.setAttribute('name', 'DuoForumHacks');
    script.textContent = '(' + f.toString() + ')(jQuery)';
    document.head.appendChild(script);
}
inject(f);

function f($) {
    function showPreview() {
        var sComment =$(this).children('a').attr('href');
        if (sComment.match("comment")) {
            var sUrl = $(location).attr('protocol') + $(this).children('a').attr('href').replace('comment', 'comments');
            var $hCurrLink = $(this);
            if ($hCurrLink.attr("data-original-title") === undefined) {
                $hCurrLink.attr({"data-placement": "auto", "data-original-title": "Loading preview"});
                $hCurrLink.tooltip('show');
                $.ajax({dataType: "json", url: sUrl}).done(function (data) {
                    var sMsg = (data.message.substring(0, 100) + " ...");
                    if (data.translation) {
                        sMsg = (data.translation.substring(0, 100) + " ...");
                    }
                    $hCurrLink.attr({"data-placement": "auto","data-original-title": sMsg});
                    $('.tooltip').attr({"white-space": "pre-wrap","max-width": "200px","min-width":"200px"});
                    $('.tooltip-inner').text(sMsg);
                }).error(function (xhr, ajaxOptions, thrownError) {
                    $hCurrLink.attr({"data-placement": "auto","data-original-title": "Error ("+xhr.status+") loading preview. "});
                    $('.tooltip-inner').text("Error ("+xhr.status+") loading preview. ");
                });
            }
        }
    }
    function loadQuotes($currComment){
        if( !$currComment.children(".footer a").hasClass('customquote')){
            if ($('#app').hasClass('community-topic') ) {
                var $hQuote = ('<a class="customquote" href="javascript:;" >Quote</a>');
                $currComment.children(".footer .divider").before($hQuote);
            }         
        }
        $("div.footer").on('click','.customquote',function(e){           
            var oParent= $(this).closest('li');
            var bCanReply = oParent.find('.footer a').hasClass('add-reply');
            var sPosterName=oParent.find('a.username')[0].innerHTML;
            sPosterName = "["+sPosterName+"](/"+sPosterName+")";
            var sCommentText= oParent.find('bdi')[0].outerText;
            if (!bCanReply) {
                oParent = oParent.parent().closest('li');
            }
            var sTextAreaId = oParent.find('.textarea-block:first');
            sTextAreaId.parent().attr('style','display:block;');
            $(sTextAreaId ).val(sPosterName+' wrote:\n\n'+sCommentText+'----');
            $(sTextAreaId ).attr('style','overflow: hidden; word-wrap: break-word; resize: none; height: '+($(sTextAreaId )[0].scrollHeight+4)+'px');
        });
    }
    
    $('body').on("mouseenter", ".list-discussion-item-header", showPreview);
    $('body').on("mouseenter", ".stream-item-content", showPreview);
    //$('body').on('mouseover', ".discussion-comments-list-item", function (){ 
    // loadQuotes($(this));
    //});
    $('body').on('mouseover', ".footer", function (){ 
        loadQuotes($(this));
    });
    $('body').on('mouseover', ".add-reply", function (){ 
        loadQuotes($(this));
    });
    
    $('body').on('mouseleave', ".footer", function (){
        $('a.customquote').remove();
    });
}