Unable to add Inline comment (plain text)

Steps to reproduce:

1. Create a new page.
2. Import a word document.
3. Mark some plaintext (no macro or user mention visible) and create an inline comment.
4. Save the page.

Expected Results:
Comment should be saved.

Actual Results:
The following alert shows up and the comment is not saved.

Alert:
We can't add your inline comment; the section you highlighted may contain a macro or user mention. Try highlighting plain text.

Note: Even if I retype the affected word ("West-Balkan") in another part of the page, the result is still the same.