[texhax] Odd behavior in a \mathop

[Michael Barr]

If you compile the file
\documentclass{article}
\newcommand\II{\mathop{I\mkern-1mu I}}
\newcommand\I{\mathop{I}}
\begin{document}

$AB\II L$

$AB\I L$

\end{document}

you will see (or I do anyway) that the I in the second, but not the first, 
formula is going distinctly below the line.  What is going on here?  If 
you take out the \mathop this does not happen.

Michael Barr