Hello! If you don't mind me asking, what browser are you experiencing this issue on?

All done with US International, but should be reproducible with other keyboard layouts; just that with, e.g. a German layout it might be harder to find digraphs that can be typed by forcing a non-combination for a dead key.

Firefox 81, Windows: Dead keys and the corresponding combination of letters where no single letter is defined by the keyboard layout don't even appear. I.e. I type ', and then s, which normally causes the digraph 's to appear, but here neither the ' nor the s afterwards register.

Chrome 85, Windows: The key sequence registers as just one letter, but apparently not as the ', which thus is marked as an error. This was also what I've seen in Edge (Chromium-based, probably similar version number).

Internet Explorer 11: Same as with Chrome. However, with the added bonus that typing a space seems to be impossible. No idea whether that browser is even on the compatibility list for that site, but it's all I have lying around here right now.

Thanks for your very descriptive answer! At the moment, key combinations aren't nearly as well supported as they ought to be. I'll certainly fix this in a future update. Thanks again!