It is one of the things I like about Colemak that it takes into account QWERTY's dominance in computers and intentionally doesn't move a lot a shortcut keys and punctuation. Semicolon is the most obvious punctuation mark that does move, most of the rest stay where they are. The big list of shortcut keys that stay the same place includes AZXCVBMWQ. XCV not moving is especially a big deal, as you also mention copy and paste as key shortcut examples.

In general Colemak doesn't move keys to radically far from their QWERTY positions (many stay on the same finger, even), so I've heard using it and QWERTY together isn't too bad. In my personal case, I had a terrible QWERTY form and realized I don't have to do anything but "hunt-and-peck" in QWERTY when using other people's machines. I may feel a bit like an idiot doing it, but it turns out, most people don't even notice if you touch type or hunt and peck (partly because so many more people hunt and peck than you tend to realize; even in a world where QWERTY touch typing has to be taught in schools, I think it is still a skill like Cursive that you think everyone else uses once you learn it, but you forget how hard it was to learn in the first place). It's more "my guilt" that I "use QWERTY poorly" than anything anyone else actually cares about.