One of the big user error issues that comes to me as an admin is misuse due to misunderstanding of the Copy To feature. Too often we have teachers who use Copy To in order to duplicate materials in the same Canvas course (I spent nearly 2 hours today helping just 1 teacher fix modules in 6 courses). I think part of the confusion stems from the fact that duplicate doesn't always show up in the menu, you can't duplicate a module, and external tool assignment, etc, so teachers select the next logical thing in that menu, Copy To. The next problem in the workflow arises from the fact that you can select the current course from the list of course. Teachers then go on to copy Assignment 1 from Module 1 into Module 2. They edit the assignment, thinking it is Assignment 2 and a unique copy, only to discover at some later point that Assignment 1 and Assignment 2 both show the same updated content. Teachers panic, if it's a page we can restore via the page history, if it's an assignment and past the last beta reset, we've lost that prior work, and they need to redo. I can only assume this is also a somewhat frequent issue the comes to Canvas Support as well.
Yes, this is all in the guides, but there are a million guides to go through and teachers are already overwhelmed with information right now. A simple, quick-to-implement solution would be to add a warning statement in the Copy To panel. Ex. something telling teachers not to copy into the current course, or that copying into the current course will not create a second resource. Alternatively, a less simple solution would be to update the the logic that populates the drop-down list of courses so the the current course cannot be selected.