Thank you for getting to us with this!
I will comment on your questions successively.
Regarding the first question about the zero based ordering, indeed this is a bug in RadRichTextBox. I logged the issue in our to-do list and we will do our best to fix it as soon as possible. I’m afraid that the only possible way to solve it is to modify your existing HTML. You should set the “start” attribute of the nested <ol> list to 1.
As to your second question about adding <li> tag around the nested lists, this is a known behavior but our investigation shows that it works correctly in all modern browsers (Internet Explorer as well). Currently, there is no way to prevent adding this tag. This issue is already added in our to-do list. At this point the implementation of this is not scheduled.
The Telerik points in your account have been updated in appreciation of your involvement.
Let me know if you have other comments or questions.