Updated the comments about sharing an interpolator between LM UV and vertex SH in LW.

ScriptableRenderPipeline/LightweightPipeline/LWRP/Editor/ShaderGraph/lightweightPBRForwardPass.template

 		float3 lwWorldPos = TransformObjectToWorld(v.vertex.xyz);
 		float4 clipPos = TransformWorldToHClip(lwWorldPos);
 
- 		// We either sample GI from lightmap or SH. lightmap UV and vertex SH coefficients
-	    // are packed in lightmapUVOrVertexSH to save interpolator.
-	    // The following funcions initialize
+ 		// We either sample GI from lightmap or SH.
+	    // Lightmap UV and vertex SH coefficients use the same interpolator ("float2 lightmapUV" for lightmap or "half3 vertexSH" for SH)
+        // see DECLARE_LIGHTMAP_OR_SH macro.
+	    // The following funcions initialize the correct variable with correct data
 	    OUTPUT_LIGHTMAP_UV(v.texcoord1, unity_LightmapST, o.lightmapUV);
 	    OUTPUT_SH(lwWNormal, o.vertexSH);
 

ScriptableRenderPipeline/LightweightPipeline/LWRP/ShaderLibrary/LightweightPassLit.hlsl

     // initializes o.normal and if _NORMALMAP also o.tangent and o.binormal
     OUTPUT_NORMAL(v, o);
 
-    // We either sample GI from lightmap or SH. lightmap UV and vertex SH coefficients
-    // are packed in lightmapUVOrVertexSH to save interpolator.
-    // The following funcions initialize
+    // We either sample GI from lightmap or SH.
+    // Lightmap UV and vertex SH coefficients use the same interpolator ("float2 lightmapUV" for lightmap or "half3 vertexSH" for SH)
+    // see DECLARE_LIGHTMAP_OR_SH macro.
+    // The following funcions initialize the correct variable with correct data
     OUTPUT_LIGHTMAP_UV(v.lightmapUV, unity_LightmapST, o.lightmapUV);
     OUTPUT_SH(o.normal.xyz, o.vertexSH);