Unable to delete non editable element in IE8

[Irina]

Steps to reproduce:

1. Open Full Page Editing
2. Delete all content in the editor
3. Copy following into Source tab:

<span contenteditable="false"><a href="https://test.com">test</a></span>

4. Switch back to Rich Text editing
5. Copy link from left to right
6. Press Backspace

Result: Link not deleted

If you will select the same link form right to left then backspace will delete it.

[Jakub Ś]

This one took me while to reproduce:

1. First problem was fixed #5562
2. Next there was fix presented in #5801. This fix has broken moving cursor behind non-editable element.
3. Next after rev. [7374] selecting and deleting non-editable element with Backspace key acted as Browser Back Button.
4. Finally after rev. [7600] "back button" behaviour was changed to not deleting anything like in TC mentioned by @irina.

[Piotrek Koszuliński]

I think that this ticket should be closed for the same reason as #12128. Since CKEditor 4.3 widget system should be used to handle non-editable content inside editor.

However, I anticipate that you haven't used widget system for a reason. Could you elaborate more on that?