% Minimum working example of a bug in 'memoir.cls':
% 'marginpar{<short comment>}' breaks 'sidebar{<multipage comments>}'
% The bug is that the order of the lines in the sidebar is jumbled.

documentclass[9pt,A4]{memoir}

%  --- header of the log file -----------------------------------------
%  This is pdfTeX, Version 3.14159265-2.6-1.40.18 (TeX Live 2017)
%      (preloaded format=pdflatex) restricted write18 enabled.
%  entering extended mode
%  (./memoir_bug_in_sidebar.tex
%  LaTeX2e <2017-04-15>
%  Babel <3.15> and hyphenation patterns for 84 language(s) loaded.
%  (/usr/local/texlive/2017/texmf-dist/tex/latex/memoir/memoir.cls
%  Document Class: memoir 2016/05/16 v3.7f configurable
%      book, report, article document class
%  --------------------------------------------------------------------
%  Note: no very evident errors are reported in log file ...

% load packages
RequirePackage{xcolor}
RequirePackage{ragged2e}
RequirePackage{calc}
RequirePackage{lipsum}

%  --- begin memoir/sidebar/marginpar adjustments -------------
%  note: details of these appearance-options seemingly are
%        immaterial to the sidebar{...} wrap-bug

%  set and check the page dimensions
%  preparing for marginparwidth = 11em
%                  sidebarwidth = 14em
normalfont%
setlrmarginsandblock{11em+1em+2cm}{14em+1em+2cm}{*}
checkandfixthelayout

%  adjust the marginpar parameters
marginparmargin{inner}
setmarginnotes% {<hsep>}{<width>}{<push>}
  {1em}%                    specify  <hsep> => marginparsep
  {spinemargin-1em-2cm}%   specify <width> => marginparwidth
  {onelineskip}%           specify  <push> => marginparpush

%  adjust the sidebar parameters
sidebarmargin{outer}
setsidebars% {<hsep>}{<width>}{<vsep>}{<topsep>}{<font>}{<height>}
  {1em}% specify <hsep>
  {foremargin-1em-2cm}%    specify  <width> => sidebarwidth
  {onelineskip}%           specify   <vsep> => sidebarvsep
  {0pt}%                    specify <topsep> => sidebartopsep
  {sffamilyfootnotesize%  specify the <font> parameters
      % BUG: the following 'color{...}' bleeds into the body
      color{blue}}%           (optionally including a color)
  {textheight}%            specify <height> => sidebarheight
DeclareRobustCommand{sidebarform}{justifying}
%  --- end memoir/sidebar/marginpar adjustments -------------

begin{document}
textbf{This is the first paragraph of a
multipage memoir-class document.}

lipsum[2]%
marginpar{
    Marginal comments like this one,
    when they comes textsc{before}
    a multipage sidebar,
    textsc{do not} induce a wrap-error.
}

lipsum[3]%
sidebar{strictpagecheck%
    textbf{TEST: this sidebar paragraph should
    appear on page 1, at the top of the fore-margin.}
    par
    lipsum[2-11]
    par
    textbf{TEST: this sidebar paragraph should
    appear as the bottom-most fore-margin
    paragraph, as the final paragraph
    (namely the 12th paragraph)
    of a multipage sidebar.}
}%

lipsum[4]%
marginpar{strictpagecheck%
     textsc{Alas}dots marginal
    comments like this one,
    that are specified textsc{after}
    a multipage sidebar,
    textsc{do} induce a wrap-error.
}

lipsum[5-8]%

lipsum[9]%
marginpar{strictpagecheck%
    textsc{Alas}dots this marginal
    comment too, appearing
    on the second page of
    a multipage sidebar,
    induces a wrap-error.
}

lipsum[10-19]

textbf{This is the final body-text
paragraph (namely the 20th paragraph)
of a multipage document.}

end{document}
endininput