Exactly what it looks like.
// ==UserScript==
// @name Selectable text on FF.net
// @description Exactly what it looks like.
// @namespace asdf
// @match http://www.fanfiction.net/*
// @match https://www.fanfiction.net/*
// @version 1
// @grant GM_addStyle
// ==/UserScript==
GM_addStyle(" .storytext, .storytextp \
{ \
-moz-user-select: inherit !important; \
-webkit-user-select: inherit !important; \
user-select: inherit !important; \
}");