The full screen version is going to be browser dependent on whether or not you can copy and paste it since it is using the standard browser "alert" feature. The bigger one you see on the Map Detail page is loaded by all the other stuff we have going on there. We want the public versions to not have any MME styling for people who are embedding it.
The copy and pasting is working for all the computer we have tested it on, Mac and Windows.
When sharing maps, make sure you are using the public version that has "public" in the url instead of "detail".