The behavior you describe sounds very strange.
The copy/paste feature works the same, regardless of the app, or even email address used.
I have been trying to reproduce the behavior you describe, but unsuccessfully. The main reason being, that the 'copy' button does not appear when I want to paste something, because 'copy' only appears when text is selected and pressing for a while does not automatically select text, it just shows the blue vertical bar while asking what to do next.
While this does not really answer your question, it might be noteworthy to add, that I can copy text from AuthorJotter and paste it into gmail emails without problems.