Tuttavia
`\documentclass[a4paper,12pt]{article}
\usepackage[T1]{fontenc}
\usepackage{fontspec}
\usepackage{amsmath}
\usepackage[math-style=upright]{unicode-math}
\setmainfont[Ligatures=TeX]{TeX Gyre Pagella}
\setmathfont{Asana Math}
\usepackage{polyglossia}
\setmainlanguage{italian}
\usepackage{microtype}
%\newcommand\ap[1]{\textormath{\textsuperscript{#1}}{^{\mathrm{#1}}}}
%\newcommand\ped[1]{\textormath{\textsubscript{#1}}{_{\mathrm{#1}}}}
\providecommand*\ap[1]{\textormath{\textsuperscript{#1}}{_{\mathrm{#1}}}}
\providecommand*\ped[1]{\textormath{\textsubscript{#1}}{^{\mathrm{#1}}}}
\begin{document}
\begin{equation*}
p \leftrightarrow q
\end{equation*}
bla bla
\begin{equation}
p \leftrightarrow q
\label{equ:coimplicazione}
\end{equation}
bla bla
\begin{equation}
p \leftrightarrow q \tag{D\ped{2}}
\label{equ:D\ped{2}}
\end{equation}
\end{document}}`
mi dà errore:
`
! Missing \endcsname inserted.
\bgroup
l.8 …qu:D^{\mathup {2}}}{{{D^{\mathup {2}}}}{1}}
?
`
Impossibile avere il pedice anche in label?
m