The root cause is that separators are detected by keyCode (physical key) rather than by the typed character. The UI language and the keyboard layout are independent, so a locale-based exception can't cover all cases (e.g. English UI with a Ukrainian layout). The same applies to the Italian case from 0003513 ("@" on the ";" key).

Suggested fix: treat keyCode 186/188 as separators only when the typed character is actually ";" or "," (event.key).

Working workaround, tested on our server, loaded via SOGoUIAdditionalJSFiles (in mailcow: data/conf/sogo/custom-sogo.js):

(function () {
window.addEventListener('keydown', function (e) {
if ((e.keyCode === 188 || e.keyCode === 186) &&
e.key !== ',' && e.key !== ';' &&
e.target && e.target.closest &&
e.target.closest('md-chips, md-contact-chips')) {
e.stopPropagation();
}
}, true);
})();

The listener runs in the capture phase and stops the keydown event before it reaches md-chips, but only when the physical key is comma/semicolon and the typed character is not. The letter is inserted normally, and "," / ";" typed on the Latin layout still work as separators. Verified with Ukrainian and English UI languages.

Environment: SOGo 5.12.10, mailcow 2026-07b, browser chrome / OS Windows&Linux