Comma missing from superiors

[juhaszp95]

The bug
The comma (' , ') is missing from the set of superiors. It would be nice to have a comma there besides the letters and numbers, as this is sometimes used to note the affilications of authors in publications, like Foo^1,2.

Steps to reproduce
MWE (in LuaLaTeX):

\documentclass[12pt]{article}
\usepackage{libertinus-otf}

\begin{document}
	Foo\textsup{1,2}
\end{document}

Expected vs actual behavior
I'd like to see a superior comma between the superior 1 and 2. Instead, I get a normal (lower) comma.

Screenshot
Output of the MWE:

[hvoss49]

You can use simple footnotes or package biblatex, if you want to use \footcite

\documentclass[12pt]{article}
\usepackage[multiple]{footmisc}

\begin{document}
	Foo\footnote{foo}\footnote{bar}
\end{document}

[juhaszp95]

Well, in this case the corresponding text is just set in normal size, just below the authors. This is standard practice in physics journals, see e.g. https://arxiv.org/pdf/2011.10536.pdf. So I would really need a superior comma.

[hvoss49]

For example:

\documentclass{article}

\usepackage[a4paper]{geometry}
\usepackage{libertinus-otf}

\title{foo${}^{1,2}$ and bar${}^2$ \\[\bigskipamount]
	{\Large\mdseries\parbox{\linewidth}{\hangindent=1em 
	 ${}^1$\,Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, 
	    United Kingdom

	 \hangindent=1em   
	 ${}^2$\,Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, 
	    Cambridge CB3 0HE, United Kingdom \par}}}
\date{}
\begin{document}
	\maketitle
\end{document}

[juhaszp95]

Thanks for this proposal - although at that point I can simply use \textsuperscript{1,2} which gives almost the identical result - neither of which are from the sups series. So there are ways around this for sure, I just wanted to flag that perhaps the comma could be implemented in sups proper.