On Sunday I was working on a Sermon Doc and copy / pasted the contents of a Note into the document.
I then found that I couldn't edit the pasted text - in that I couldn't add new text to it. If I tried to delete an individual character the entire containing paragraph was deleted.
I was able to use Cmd-X to cut portions of the text and Cmd-V to paste in additional words.
On Sunday I was using Safari on a Mac and I've just reproduced this behaviour using Chrome on Windows 10.
If I paste the text from the Note into Wordpad and then copy / paste that into a Sermon Doc I can edit it without any problem.
It looks as though a straight copy / paste from the Notes Tool is bringing across some formatting information.