This is very helpful. I did some experimenting. In each case I pasted into the WordPress Visual Editor:
Text with hyperlinks copied in Chrome:
Pasted in Firefox with Cmd-V: hyperlinks retained
Pasted in Firefox with Edit menu "Paste": "paste" grayed out if you've already pasted, but if you paste right after copy, hyperlinks retained
Pasted in Chrome with Cmd-V: hyperlinks stripped out
Pasted in Chrome with Edit menu "Paste": hyperlinks retained
Pasted in Safari with Cmd-V: hyperlinks retained
Pasted in Safari with Edit menu "Paste": hyperlinks retained
Pasted in Mail with Cmd V: hyperlinks stripped out but font copied
Pasted in Mail with Edit menu "Paste": hyperlinks retained and font also copied
Text with hyperlinks copied in Firefox:
Pasted in Firefox with Cmd-V: hyperlinks retained
Pasted in Firefox with Edit menu "Paste": "paste" grayed out if you've already pasted, but if you paste right after copy, hyperlinks retained
Pasted in Chrome with Cmd-V: hyperlinks stripped out
Pasted in Chrome with Edit menu "Paste": hyperlinks retained
Pasted in Safari with Cmd-V: hyperlinks retained
Pasted in Safari with Edit menu "Paste": hyperlinks retained
Pasted in Mail with Cmd V: hyperlinks stripped out but original font retained
Pasted in Mail with Edit menu "Paste": hyperlinks retained but default Mail font used
Text with hyperlinks copied in Safari:
Pasted in Firefox with Cmd-V: hyperlinks stripped out
Pasted in Firefox with Edit menu "Paste": hyperlinks stripped out
Pasted in Chrome with Cmd-V: hyperlinks stripped out
Pasted in Chrome with Edit menu "Paste": hyperlinks retained
Pasted in Safari with Cmd-V: hyperlinks stripped out
Pasted in Safari with Edit menu "Paste": hyperlinks stripped out
Pasted in Mail with Cmd V: hyperlinks stripped out
Pasted in Mail with Edit menu "Paste": hyperlinks retained
I confess I do not understand the difference between "Paste" and "Cmd-V" but they do act differently, and of course in some parts of Mail (e.g., the "To" field) Cmd-V does not work at all and you must use "Paste."
It's strange that Firefox won't accept the hyperlinks in Safari-copied text but does fine with Chrome-copied text and Firefox-copied text.