Don't know if this is a bug or a feature. Can't believe no one's noticed it, but I couldn't find any mention, so here goes...
When dragging files to tabs, it seems that if the target tab/directory is on a different drive (local logical, physical, or networked), the copy indicator -- the plus-in-a-box -- is displayed, as it should be for copy operations. However, the copy indicator does not go away with the shift modifier to move the files instead of copy. The move and copy actions both work correctly.
Other observations:
• The behavior is the same in any view mode
• The move/copy indicators are correct when dragging into window panes
Maybe you checked the option "move files instead of copy, if it is on the same drive". Sorry, i looked for minutes, but just can´t find the exact location in the preferences.
I've seen that feature somewhere (I couldn't find it just now, either), but that shouldn't have anything to do with the issue I was talking about. That setting simply toggles the default Windows copy/move behavior, and that's not what I meant.
When you drag copy something, you should get the plus-in-a-box indicator as per standard Windows behavior. If you hold the shift key while doing a drag copy, the plus-in-a-box goes away to indicate that the operation has changed to move.
What I was trying to say in the initial post is that when I drag files to tabs where the directory is on a different drive, the plus-in-a-box is ALWAYS there, even when holding down shift and moving the files.