Rename amsthm proof environment but retain dot

Question

I am following the directions from this SE question to change the text in an amsthm "Proof" to 증명, which is the Korean word for the same.

If I put in Latin text, it works just fine.

\documentclass[12pt]{article}
\usepackage{amsthm}
\usepackage{kotex}
\renewcommand*{\proofname}{My proof}
\begin{document}
\begin{proof}
To get a contradiction, suppose that $3 = 4$. 
\end{proof}
\end{document}

prints My proof. To get ... However, changing the third line to

\renewcommand*{\proofname}{증명} 

prints 증명 To get a contradiction, suppose that 3=4. with the dot missing. On the other hand,

\renewcommand*{\proofname}{증명.} 

prints 증명.. To get a contradiction, suppose that 3=4. with two dots!

How do I get just one dot?

Answer 1

I can reproduce the issue with pdflatex, but not with XeLaTeX or LuaLaTeX.

The reason is that the space factor after Korean characters is set to 1001: it is used for deciding whether breaking before Hangul at transitions, I believe.

However, this conflicts with \@addpunct that adds its argument only if the current space factor is 1000 or less.

Solution: add \@

\documentclass[12pt]{article}
\usepackage{amsthm}
\usepackage{kotex}
\renewcommand*{\proofname}{증명\@}
\begin{document}
\begin{proof}
To get a contradiction, suppose that $3 = 4$. 
\end{proof}
\end{document}