Operating system: Win10
Graphics card: 2x 1080 Ti
Broken: 2.80 Beta, 54ffc4e19dc4
Short description of error
As the title says: Parenting to a bone offsets the mesh. The mesh doesn't have any tranformation or any other offset-creating effect/animation applied.
One thing which helped: checking the Relative Parenting checkbox positions the object back to the starting position.
Exact steps for others to reproduce the error
Start a new Blender file, 3D cursor should be at the world origin, create a mesh (doesn't matter which one), create an armature (automatically you get one bone). Parent the mesh to the bone, see how the mesh get transformed.