Try: using \letterhash instead of \# or \startasciimode
\def \FrontMatterTitle { \startreusableMPgraphic{frontmattertitle:\overlaywidth:\overlayheight} matter_paper_width := 4.25in; matter_paper_height := 6.875in; front_left_margin := 0.388888888889in; top_margin := 0.347222222222in; draw (0, 0)--(matter_paper_width, matter_paper_height) withpen pencircle scaled 1bp withcolor white; picture titleText;
%% == HERE IS THE SOURCE OF THE PROBLEM ==
titleText := btex {\vbox{\hsize 2.72916666667in \baselineskip 38.0pt \setupalign[flushleft,hyphenated,verytolerant] \TitleFont THE BEGINNINGS OF #BOOM}} etex; %%%%%% NOTE I changed \# to # and % to %% labeloffset := 0bp; label.lrt(titleText, (front_left_margin, matter_paper_height - top_margin)); \stopreusableMPgraphic \reuseMPgraphic{frontmattertitle:\overlaywidth:\overlayheight} }
\stopasciimode You can also use \framed[width=2.73in, foregroundstyle={\TitleFont\setupinterlinespace[38pt], align={flushleft, ....}]{The ....} instead of explicit \vbox. Aditya