If the DEL key is pressed at the end of Row 1.1.1

- Row 1
  - Row 1.1
    - Row 1.1.1
- Row 2
- Row 3


then it looks like this (with two slashes -)


- Row 1
  - Row 1.1
    - Row 1.1.1Row 2
- - Row 3

This is the answer from Telerik:
I am afraid the result of the delete key press comes entirely from the browser. You can check out this example here: http://dojo.telerik.com/ejEfu. If you repeat the same steps, you will get the same results. This is how the browser interprets the deletion with del key in this scenario. 
The Kendo Efitor does not somehow interrupt the browser deletion functionality and currently has no control over the content that is deleted and replaced. You could possible suggest a feature request on the topic in the Kendo Feedback channel so that others can vote for your suggestion. The solution of that case would be the deletion commands to be controlled via custom editor commands (something that is not present currently).

Bug report

Copied text is pasted with some (editor's ?) styles.

Steps to reproduce

1. Open the Demo page in the Edge browser:

https://demos.telerik.com/kendo-ui/editor/index

2. Copy some words (e.g. "Kendo UI Editor") from the editor's default text.

3. Paste them at the end of the text.

4. Open developer tools (F12).

5. On the Elements tab, select the pasted paragraph and check its style, you will see <span style="display: inline !important; etc.