This topic is already discussed in the support ticket opened by you (880916
). Please, let us continue the conversation there as we have already started it.
For anyone other interested on the matter, the suggestion is that this is entirely a browser behavior. Specific content transfer trough the clipboard is entirely controlled by the desktop applications and in this particular case, the browser. Moreover, as stated by James, SharePoint runs under IE compatibility mode due to browser compatibility matters.
By that, this appears to be more a result of browser support matter. And such type of data is being properly transferred under modern browser, although in earlier versions there is no such content support, so that it could be properly pasted in the editor's content or any other plain content editable DOM element.
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