Incidentally, this is no longer necessary. Gwern.net used the same trick but we removed it last week (to much rejoicing).
The main reason to auto-add soft hyphens is because, unlike almost all other browsers, desktop Chrome has for decades not supported hyphenation (even though mobile Chrome does!). But they finally shipped support last year, and now market support for hyphenation is around 95%+ according to CanIUse. So you can just drop the soft hyphen pass and rely on normal CSS to specify justification.
This is good because it simplifies HTML creation, makes the HTML noticeably smaller & better compressing, makes it more readable, search/replace more reliable, buggy screen readers no longer pronounce soft hyphens (another real WTF moment for me), doesn't require hacks like the JS copylistener to strip them out...
Anyway long story short, if you've been using the soft hyphen trick, I suggest revisiting the decision now.
The main reason to auto-add soft hyphens is because, unlike almost all other browsers, desktop Chrome has for decades not supported hyphenation (even though mobile Chrome does!). But they finally shipped support last year, and now market support for hyphenation is around 95%+ according to CanIUse. So you can just drop the soft hyphen pass and rely on normal CSS to specify justification.
This is good because it simplifies HTML creation, makes the HTML noticeably smaller & better compressing, makes it more readable, search/replace more reliable, buggy screen readers no longer pronounce soft hyphens (another real WTF moment for me), doesn't require hacks like the JS copylistener to strip them out...
Anyway long story short, if you've been using the soft hyphen trick, I suggest revisiting the decision now.