I've come here to ask the same thing. I get the following messages/toasts if I copy a link in WhatsApp: Link copied. Copied to clipboard. Link copied. This is too distracting and prevents me from pasting asap. It also is 9 seconds of my time.
I'm using the SwiftKey keyboard (though same behaviour with the Samsung keyboard), I've disabled Alert when clipboard accessed, Time to take action is set to Default and I have disabled syncing as far as I can tell...