Thanks for the detailed feedback!
We’ll investigate the copy/paste issue. Odd.
We’ll also take a look at interaction with the text editor. I expect a lot of it is standard behavior cooked into Apple’s frameworks. I don’t think we do a lot to affect the basic interaction, but maybe there is something we changed.
Dark/light text is a bit tricky, I guess. You should always get the right color if you paste and match style. Otherwise the original color of the text will be included, and then it might look wrong if the UI is not the correct setting.