pssst, that's just smoothinggroups.
(having none at all assigned makes unreal apply 1 to everything)
make sure you make proper lightmap UVs.
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Not sure the .skp->.ase exporter thinks about smoothing at all, probably going to be a pain to fix.
autosmooth with low value, should work.
also, .ase (or unrelengine itself, not sure) doesn't support multiple smoothinggroups per face.
keep that in mind when you do your smoothing.
(unless they improved that later on, since this was at least the case with UT3)
From what I can tell, Sketchup only applies a smoothing group to the edges that are within angle parameters for the smooth operation, so that doesn't really work.
Last I read .fbx had support for multiple smoothing groups on import. I could be wrong though.
did a little research, but couldn't really find any documentation on unreal only supporting 1 SG per face. (though i'm pretty sure of this)
you'd be best off doing a simple test-mesh.
the thing i did find confirmation on, is that unreal needs a smoothinggroup applied to EVERYTHINg, otherwise it'll create one for you (usually bad)
I do know that you can eliminate some of the weird lighting issues with a second UV for lighting and using normal maps that have crisp edges and are totaly flat on the faces of the model.