**System Information**
Operating system: Windows-10-10.0.18362 64 Bits
Graphics card: GeForce GTX 1080 with Max-Q Design/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 436.48
**Blender Version**
Broken: version: 2.81 (sub 13), branch: master, commit date: 2019-10-03 17:34, hash: `rB6ac2a2061f8b`
**Short description of error**
Unparenting a mesh that also contains an armature modifier removes the modifier
**Exact steps for others to reproduce the error**
Hit Alt+P {F7799766}
The armature modifier will be gone after unparenting.
An unparent operator is NOT about modifiers. It's about hierarchy.
A rig is not necessarily defined by an armature modifier in a mesh pointing to an armature. There can be more complex relationships between different types of objects and modifiers. Clearing the armature modifier like it somehow makes it "unparented" assumes the most basic of relationships only and would be breaking rigs unpredictably since the user never asked for that explicitly. (What about mesh deform modifiers? Multiple armature modifiers? etc etc)