I can reproduce the "problem", but there is a misunderstanding... what you see around the pasted object is not the layer boundary, it is an automatic alpha-to-selection applied to what is being pasted. The true size of the initial copy is still there, in particular, at that point "Layer>To new layer" will create a layer the size of the initial selection. In the picture below, I made a wide selection around a funky shape with partial opacity, and notice that:
1) in the target window the selection goes over the partial opacity areas of the shape (I'd bet my money that this is where the shape is 50% transparent)
2) the distance between the left edge of the shape and the left guide is exactly the size of the transparent margin in the source copy. This because I moved the floating selection and let it snap to the guide (and what snaps is the layer boundary, even if you don't see it).
So what is required is either:
1) in the target window the selection goes over the partial opacity areas of the shape (I'd bet my money that this is where the shape is 50% transparent)
2) the distance between the left edge of the shape and the left guide is exactly the size of the transparent margin in the source copy. This because I moved the floating selection and let it snap to the guide (and what snaps is the layer boundary, even if you don't see it).
So what is required is either:
- a bit of faith because even if you don't see it, the copy boundary is there
- and if you want to see it, Ctrl-Shift-N to make a new layer from the copy, and it will have the initial copy boundary