EQ is totally right. But if you want to be really hacky, you could lock all your vertex normals before doing the extra geometry cuts, then manually edit the vertex normals of the vertices you added to match the original geometry. That way you don't have to re-bake at all and you shouldn't have any visible artifacts. It is…
If you want it to look correct then yes you will have to rebake. The bake accounts for the exact vertex normals of your mesh, so when you go in adding/removing verts you're changing the smoothing etc and break the normals map. Some times you can get away with this, say if you have a simple cylinder type object with hard…