Try non-Computer Modern font.

This commit uses URW Schoolbook L

http://www.tug.dk/FontCatalogue/urwschoolbookl/

subsuper-proposal.tex

@@ -9,6 +9,9 @@
 \usepackage{amssymb}
 \usepackage[unicode=true]{hyperref}
 
+\usepackage{fouriernc}
+\usepackage[T1]{fontenc}
+
 \usepackage{todonotes} %XXX REMOVE ME WHEN DONE
 \newcommand{\TODO}[1]{\todo[inline]{#1}}
 
@@ -136,7 +139,7 @@ \section{Proposed Additions to Subscript/Superscript Characters}
 Should we also ask for the italic ($\mathit{{X}}$), bold ($\mathbf{{X}}$),
 and bold-italic ($\mathbf{\mathit{\boldsymbol{{X}}}}$) variants?
 Script variants like $\mathscr{X}$, and blackboard-bold variants
-like $\mathbb{{X}}$? Or is this asking for too much?
+like $\mathbb X$? Or is this asking for too much?
 
 What other math symbols are commonly used as super/subscripts? $\Vert,\perp,*,\dagger,\ldots$
 ?