windows 8.1 surface pro intel HD 4000 ;
windows 7 nvidia geforece Gtx 560
Short description of error
viewport does not update shading of model while sculpting on meshes with matcap set throught shadeless material with texture mapped to normal and Autosmoth checkbox checked in Normals section of object Data.
Exact steps for others to reproduce the error
Create suzanne, add material in Blender Internal and check shadeless in shading section, go to texture tab. Add texture and choose any of this round ball images like here
go to mapping section and choose normal from coordinates section. Then go to object Data tab and check autosmooth checkbox.
Then add multiresolution subdivide few times, go to sculpt mode and start sculpting. Shading of model will update only if you exit sculpt mode and move back to sculpt mode.