Deleted style incorrectly remembered

[zacaway]

Refer to the attached video for demonstration, but this can be easily reproduce on the demo CKEditor at ​http://ckeditor.com/demo as follows:

1. click to enter the editor
2. hit bold button
3. type "bold "
4. hit italic button
5. type "italic "
6. hit strike through button
7. type "strike through"
8. hit backspace to delete the entered text, up to the middle of the word "italic"
9. start typing again
10. the text will be formatted as italic and strike through, even though there is no existing strike through text in the editor, it should be just italic (and bold, from the beginning).

[Jakub Ś]

I was able to reproduce this problem in both CKEditor 3.x and 4.x in every browser from CKEditor 3.0.