Internet Explore, Firefox, and Edge don't support the 'break-word' value for word-break in CSS.

Only Webkit based browsers support that. If you make the mistake of testing/developing primarily in Safari + Chrome, you'll never discover the error.

They might have also used 'keep-all' which isn't supported in Edge, but is supported everywhere else, and have a fallback rule of break-all leading the behavior seen.

tl;dr:

There's actually no universal way of setting word-breaks for textarea's or pseudo-textarea, so I can't imagine if that writing a rich text input field is easy considering you have no foundations to work on.