Baseline alignment of shaded side notes in the memoir class

Question

I'm using the memoir class, and I'd like to add a shaded background to my sidenotes. My solution, however, doesn't work: the baseline of the sidenote text and the body text no longer align, as illustrated by my MWE:

\documentclass{memoir}
\usepackage{xcolor}
\definecolor{shadecolor}{gray}{0.9}

\begin{document}
Lorem
\sidepar[\textit{Note.}]{}
ipsum dolor sit amet, consectetuer adipiscing elit. Ut purus elit,
vestibulum ut, placerat ac, adipiscing vitae, felis. Curabitur dictum
gravida mauris.

Lorem
\sidepar[\begin{snugshade} \textit{Note.} \end{snugshade}]{}
ipsum dolor sit amet, consectetuer adipiscing elit. Ut purus elit,
vestibulum ut, placerat ac, adipiscing vitae, felis. Curabitur dictum
gravida mauris.

\end{document}

I understand that there may be solutions provided by other packages, but I'd also like to understand why the position of the note shifts.

Answer 1

If you just want a coloured box inside your \sidepar, then you can use \colorbox{shadecolor}{<stuff>}:

\documentclass{memoir}

\usepackage{xcolor}
\definecolor{shadecolor}{gray}{0.9}

\begin{document}
Lorem
\sidepar[\textit{Note.}]{}
ipsum dolor sit amet, consectetuer adipiscing elit. Ut purus elit,
vestibulum ut, placerat ac, adipiscing vitae, felis. Curabitur dictum
gravida mauris.

Lorem
\sidepar[\begin{snugshade} \textit{Note.} \end{snugshade}]{}
ipsum dolor sit amet, consectetuer adipiscing elit. Ut purus elit,
vestibulum ut, placerat ac, adipiscing vitae, felis. Curabitur dictum
gravida mauris.

Lorem
\sidepar[\colorbox{shadecolor}{\textit{Note.}}]{}
ipsum dolor sit amet, consectetuer adipiscing elit. Ut purus elit,
vestibulum ut, placerat ac, adipiscing vitae, felis. Curabitur dictum
gravida mauris.

\end{document}