The commas appear as semicolons in my document

Question

I'm writting a simple document with a font I created and I don't know why when I use mathmode the commas appear as semicolons and the points as double points.

Here's an example:

This is the document:

\documentclass{article}

\usepackage[spanish]{babel}
\usepackage{amsmath,amsthm,amssymb,amsfonts,mathrsfs,latexsym,stmaryrd}
\usepackage{color} 
\usepackage{graphicx}
\usepackage{caption}
\usepackage{subcaption}
\usepackage{textpos}
\usepackage{enumerate}
\usepackage{xcolor}
\usepackage{titlesec}
\usepackage{float}
\usepackage{bm}

\usepackage[no-math]{fontspec}

\DeclareSymbolFont{letters}{TU}{MiLetra}{m}{n}

\usepackage{fontspec}
\newfontfamily{\miletra}{MiLetra}[
  NFSSFamily=MiLetra,
  UprightFont=*,
  BoldFont=*,
  BoldFeatures={FakeBold=3},
]

\renewcommand{\familydefault}{MiLetra}

\DeclareSymbolFont{numbers}{TU}{MiLetra}{m}{n}
\SetSymbolFont{numbers}{bold}{TU}{MiLetra}{bx}{n}
\DeclareMathSymbol{0}\mathalpha{numbers}{"30}
\DeclareMathSymbol{1}\mathalpha{numbers}{"31}
\DeclareMathSymbol{2}\mathalpha{numbers}{"32}
\DeclareMathSymbol{3}\mathalpha{numbers}{"33}
\DeclareMathSymbol{4}\mathalpha{numbers}{"34}
\DeclareMathSymbol{5}\mathalpha{numbers}{"35}
\DeclareMathSymbol{6}\mathalpha{numbers}{"36}
\DeclareMathSymbol{7}\mathalpha{numbers}{"37}
\DeclareMathSymbol{8}\mathalpha{numbers}{"38}
\DeclareMathSymbol{9}\mathalpha{numbers}{"39}

\DeclareSymbolFont{grletters}{OML}{cmm}{m}{it}

\DeclareMathSymbol{\pi}{\mathord}{grletters}{"19}

\DeclareSymbolFont{operators}{TU}{MiLetra}{m}{n}
\DeclareSymbolFontAlphabet{\mathsf}{operators}

\DeclareSymbolFont{letters}{TU}{MiLetra}{m}{n}
\DeclareSymbolFontAlphabet{\mathsf}{letters}

\begin{document}

\section{Introduction}

$(0,0)$

\end{document}

If someone knows what could I do in order to correct it I would be really thankful.

Answer 1

You should consider the unicode-math answer to your previous question, but if you go this rout you need to declare characters for the TU (Unicode) font you are using (I again switched fonts to one I had available)

\documentclass{article}

\usepackage[spanish]{babel}
\usepackage{amsmath,amsthm,amssymb,amsfonts,mathrsfs,latexsym,stmaryrd}
\usepackage{color} 
\usepackage{graphicx}
\usepackage{caption}
\usepackage{subcaption}
\usepackage{textpos}
\usepackage{enumerate}
\usepackage{xcolor}
\usepackage{titlesec}
\usepackage{float}
\usepackage{bm}

\usepackage[no-math]{fontspec}



\usepackage{fontspec}
\newfontfamily{\miletra}{Comic Sans MS}[
  NFSSFamily=MiLetra,
  UprightFont=*,
  BoldFont=*,
  BoldFeatures={FakeBold=3},
]

\DeclareSymbolFont{letters}{TU}{MiLetra}{m}{n}

\renewcommand{\familydefault}{MiLetra}

\DeclareSymbolFont{numbers}{TU}{MiLetra}{m}{n}
\SetSymbolFont{numbers}{bold}{TU}{MiLetra}{bx}{n}
\DeclareMathSymbol{0}\mathalpha{numbers}{"30}
\DeclareMathSymbol{1}\mathalpha{numbers}{"31}
\DeclareMathSymbol{2}\mathalpha{numbers}{"32}
\DeclareMathSymbol{3}\mathalpha{numbers}{"33}
\DeclareMathSymbol{4}\mathalpha{numbers}{"34}
\DeclareMathSymbol{5}\mathalpha{numbers}{"35}
\DeclareMathSymbol{6}\mathalpha{numbers}{"36}
\DeclareMathSymbol{7}\mathalpha{numbers}{"37}
\DeclareMathSymbol{8}\mathalpha{numbers}{"38}
\DeclareMathSymbol{9}\mathalpha{numbers}{"39}

\DeclareSymbolFont{grletters}{OML}{cmm}{m}{it}

\DeclareMathSymbol{\pi}{\mathord}{grletters}{"19}

\DeclareSymbolFont{operators}{TU}{MiLetra}{m}{n}
\DeclareSymbolFontAlphabet{\mathsf}{operators}

\DeclareSymbolFont{letters}{TU}{MiLetra}{m}{n}
\DeclareSymbolFontAlphabet{\mathsf}{letters}

\DeclareMathSymbol{,}\mathpunct{numbers}{`,}

\begin{document}

\section{Introduction}

$(0,0)$

\end{document}