There are good security reasons, among others to filter some unicode;

Homoglyph : https://en.m.wikipedia.org/wiki/Homoglyph

UniCode 'Confusables' Visual-Spoofing : https://unicode.org/reports/tr36/#visual_spoofing

The Invisible JavaScript Backdoor : https://certitude.consulting/blog/en/invisible-backdoor/

>There are many other characters that look similar to the ones used in code which may be used for such proposes,

  (e.g. “／”, “−”, “＋”, “⩵”, “”, “⫽”, “꓿”, “∗”). Unicode calls these characters “confusables”.<*