Well, double colon :: is just as convenient, make more sense and not a problem in either French or English. Even in English, you might want to stick an emoji to the previous word. Like Hell::devil:: (my nephew would like that though).
This stuff should just stop. Operating Systems / Browser vendors should instead standardize on a hotkey to bring up an emoji selector that steals focus to filter via typing and inserts on enter key.
Finding some sequence that also isn’t a valid Perl substring is impossible, in any case.