Steps:
1. Create a new project
2. Add a GameObject "Root"
3. Add two children to it ("Child1" and "Child2")

Hierarchy should looks like

Root
--Child1
--Child2

4. Save the scene, so it is not dirty
5. Drag "Child1" onto "Root"
==>
Child1 is placed under Child2 (wrong)
Scene is still not dirty (correct)

Expected result: No changes. Child1 keeps the position and scene is not dirty