A combination of clipboard content and editor state:
- If cliboard content is not a valid URL: the paste will act just as you said (replace any selected text or append it at the cursor otherwise)
- If the clipboard is an URL and:
- no text selected: the URL will be inserted at the cursor position
- text selected: use that text as an anchor text.
Considering that there are a few other things that doesn’t quite work as other editors (cough, cough), I’m pretty sure it wouldn’t be such a big problem for users 