Keep polypaint does exactly the same nonsense as Keep UV’s (Decimation Master), it modifies the mesh, marks the UV border on the mesh, and results in pour topology on the decimated mesh. easier when it comes to baking too.See I’ve tried it all now. If you have lots of parts keep them seperate. By isolating Polygroups it'll really help with getting at awkward parts without having to make them separate SubTools/meshes/objects etc. Those plackets were given their own Polygroups inside of ZBrush, so being able to view them in Coat would have been incredibly useful.

For instance, I've recently been working on the plackets/collar region of a jacket, but it was proving incredibly difficult to retopologize underneath them and then connect up vertices to the rest of the jacket I'd done. Or maybe some sort of hybrid of Polygroups where it recognises them from ZBrush, similar to how Maya does, which you can then customise in 3DCoat? It would be really useful to split parts of a high poly up on the fly whilst working on some retopology. I tried it with the Lasso brush/tool and couldn't split off an awkward area. I know you can currently split parts of a mesh off into their own group in the Sculpt Room, although it can be quite tricky for some areas when you have to pan the camera around and you inadvertently select parts of a mesh you don't want. I have a feature request for being able to view, isolate, separate and create Polygroups on a high poly mesh brought into 3DCoat via ZBrush. I asked about this in the general forum and it doesn't look like it's an option currently.

Zbrush polygroups