Backspace on bold, italic and underline words moves the cursor to the end of the sentence

When we have sentences that are bold ,italic, or underlined, placing the cursor over a previous text and clicking on the Backspace key on the keyboard, brings the cursor to the end of the sentence, and removes the last character instead.

How to reproduce:
1. In WYSIWYG mode, select bold, italic, or underline style.
2. Type a bunch of words to form a sentence, and make sure not to backspace on anything while typing.
3. Move the pointer/cursor over to an earlier word in the sentence, and try hitting backspace.
4. The pointer/cursor will jump/move to the end of the sentence and removes the last character instead.

Video:
bug.mov

Environment:
OS: Windows 10
Browser: Chrome, Firefox, IE

Might be related to CONFSERVER-31619