Currently, the expression in Unicode test is not recognized by the regular expressions in PHP TexVC.
A Syntax Error is thrown. If its necessary to forward such expressions through MediaWiki then the regular expressions / check functions should be updated.

Here is a gist which extracts the error case and some variations of the check without having to modify the grammar:
https://gist.github.com/Hyper-Node/04a8c5c9abf3c28a140ecd0708e9f029

• Check if the Testcase is necessary to cover in MediaWiki scenario (are unicode utf-16 chars forwarded to TexVC PHP?)
• If yes update regex or check functions