iCloud Contacts web interface on Windows - How to copy an address?
After some experimentation in different browsers I have come to the conclusion that on Firefox, the alt-click-drag action to select link text while suppressing link-follow seems to require finer mouse-cursor placement.  Start just outside the bounding box and nothing gets selected; start too far in and one character doesn't get selected.

But at least you CAN select the text.  It goes into the clipboard with each field followed by a newline, but that's a minor issue.  There really should be a "copy to clipboard" button.