I have verified this issue on the Firefox Beta 71.0b8 (Build ID: 20190919164641) (64-bit) on Windows 10, MacOS 10.14 and Ubuntu 18.04 x64. - The "Copied" state of the button is changed when the other "Copy" button is clicked.
Bug 1579260 Comment 6 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
I have verified this issue on the Firefox Beta 70.0b8 (Build ID: 20190919164641) (64-bit) on Windows 10, MacOS 10.14 and Ubuntu 18.04 x64. - The "Copied" state of the button is changed when the other "Copy" button is clicked.