Scusami, ho letto di fretta il messaggio.
Allora non usare todonotes: ci sono sempre altri modi con TikZ 😉 Il seguente, è la mia personale interpretazione di http://tex.stackexchange.com/q/49832/13304:`
\documentclass[a4paper]{scrreprt}
\usepackage{classicthesis}
\usepackage{arsclassica}
\usepackage{soul}
\usepackage{marginnote}
\usepackage{tikz}
\usetikzlibrary{calc,shadows}
% based on:
% http://tex.stackexchange.com/a/52336/13304
\definecolor{HLcolor}{RGB}{124,18,18}
\sethlcolor{HLcolor!20}
\makeatletter
\newdimen\SOUL@dimen %new
\def\SOUL@ulunderline#1{{%
\setbox\z@\hbox{#1}%
\SOUL@dimen=\wd\z@ %new
\dimen@i=\SOUL@uloverlap
\advance\SOUL@dimen2\dimen@i %\dimen@ exchanged too
\rlap{%
\null
\kern-\dimen@i
\SOUL@ulcolor{\SOUL@ulleaders\hskip\SOUL@dimen}% new
}%
\unhcopy\z@
}}
\makeatother
\newcommand\tikzmark[1]{\tikz[overlay,remember picture] \node (#1) {};}
\newcommand\MarkText[3][1cm]{%
\marginnote{\tikzmark{e}\color{HLcolor}%
\tikz[remember picture]{%
\node[drop shadow,top color=white, bottom color=HLcolor!20,rounded corners,draw,text width=0.9\marginparwidth,font=\itshape](n){#3};}
}[#1]\tikzmark{s}\hl{#2}
\begin{tikzpicture}[remember picture, overlay]
\draw[HLcolor,stealth-] let \p1 = (s), \p2 = (e) in ($(\x2,\y1)-(\marginparsep,0)$) — ($(n.north west)!0.5!(n.south west)$);
\end{tikzpicture}
}
\begin{document}
\chapter{Boh}
\section{Bla bla}
Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Ut purus elit,
vestibulum ut, placerat ac, adipiscing vitae, felis. Curabitur dictum gravida
mauris. Nam arcu libero, nonummy eget, consectetuer id, vulputate a, magna.
Donec vehicula augue eu neque. Pellentesque habitant morbi tristique senectus
et netus et malesuada fames ac turpis egestas. Mauris ut leo. Cras viverra
metus rhoncus sem. Nulla et lectus vestibulum urna fringilla ultrices. Phasellus
eu tellus sit amet tortor gravida placerat. Integer sapien est, iaculis in, pretium
quis, viverra ac, nunc. \MarkText{Praesent eget sem vel leo ultrices bibendum. Aenean
faucibus. Morbi dolor nulla, malesuada eu, pulvinar at, mollis ac, nulla. Cur-
abitur auctor semper nulla.}{I really don't understand what you are talking about} Donec varius orci eget risus. Duis nibh mi, congue
eu, accumsan eleifend, sagittis quis, diam. Duis eget orci sit amet orci dignissim
rutrum.
Nam dui ligula, fringilla a, euismod sodales, sollicitudin vel, wisi. Morbi
auctor lorem non justo. Nam lacus libero, pretium at, lobortis vitae, ultricies et,
tellus. Donec aliquet, tortor sed accumsan bibendum, erat ligula aliquet magna,
vitae ornare odio metus a mi. Morbi ac orci et nisl hendrerit mollis. Suspendisse
ut massa. Cras nec ante. Pellentesque a nulla. \MarkText[-\baselineskip]{Cum sociis natoque penatibus et
magnis dis parturient montes, nascetur ridiculus mus.}{I still don't understand} Aliquam tincidunt urna. Nulla ullamcorper vestibulum turpis. Pellentesque cursus luctus mauris.
\end{document}
`
Il risultato non è malaccio:
[attachment=935]ScreenShot2014-02-24at3.00.55PM.png[/attachment]
Ricordati di compilare 3 volte.
Ciao
Claudio