On ReactOS 0.4.15 dev-1125 g79794b5:
Horizontally moves horizontally one pixel left the layer. In the right border adds one pixel with color.
Vertically moves vertically one pixel up the layer. In the bottom last pixel adds one pixel with color.
180º moves one pixel left and one up the layer.
ReactOS Paint-specific problems that are reproduced in Windows are tracked in CORE-16634 ticket.
Attached debug log:
From ReactOS: MSPaint issue.log
However, this also happens with the 0.4.14 RC 41.