The impossible to drop thing is a bug for sure. Will get that in the queue.
The annotate borders following OP is a convenience thing to allow you to easily add OPs to your annotate area. When you hold an operator near an annotate boundary, it grows the annotate to include the operator.
Ah, looking deeper into this, I understand what’s going on. This is the same behavior as dropping a node onto another node. It doesn’t allow the drag move, preventing overlap. The entire comment area is considered the node area. For annotates, only the top bar area is considered the node area.
So this is not a bug.
If you really need to overlap in this way, the behavior only applies to dragging. You can set operator’s nodeX and nodeY positions using Python.