Why are missing characters reported as warnings and not errors? [closed]

In the following example, the PDF compiles without error using xelatex:

\documentclass{article}
\usepackage{fontspec}
\usepackage{xunicode}
\usepackage{polyglossia}
\setdefaultlanguage{english}
\begin{document}
Hello there. Do you know 𪆐 ?
\end{document}


The 𪆐 character, however, is missing in the PDF.

The log file shows:

Missing character: There is no 𪆐 in font [lmroman10-regular]:mapping=tex-text!


Why is this a warning and not an error?

closed as primarily opinion-based by Andrew Swann, Stefan Pinnow, Andrew, Mike Renfro, WernerNov 1 '16 at 13:11

Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise. If this question can be reworded to fit the rules in the help center, please edit the question.

• I suppose because this is not a syntax error. – Bernard Mar 12 '16 at 1:19
• it has nothing to do with TeX – user2478 Mar 12 '16 at 7:41
• Because the code works. The problem lies with the tool that the code is using (the font), so it's not critical. The code compiles anyway. – Alenanno Mar 12 '16 at 9:54
• Errors could be problematic. Missing characters can pop up in curious places see e.g. sourceforge.net/p/pgfplots/bugs/101 – Ulrike Fischer Mar 12 '16 at 10:10
• – ShreevatsaR Jul 1 '17 at 19:59