RelNP and ApposNP should put a final comma after the inserted phrase.

lib/src/english/NounEng.gf

@@ -22,7 +22,7 @@ concrete NounEng of Noun = CatEng ** open MorphoEng, ResEng, Prelude in {
       } ;
 
     RelNP np rs = {
-      s = \\c => np.s ! c ++ "," ++ rs.s ! np.a ;
+      s = \\c => np.s ! c ++ "," ++ rs.s ! np.a ++ finalComma ;
       a = np.a
       } ;
 

lib/src/english/ParseEng.gf

@@ -133,7 +133,7 @@ lin
   } ;
 
   ApposNP np1 np2 = {
-    s = \\c => np1.s ! c ++ "," ++ np2.s ! npNom ;
+    s = \\c => np1.s ! c ++ "," ++ np2.s ! npNom ++ finalComma ;
     a = np1.a
   } ;
   

lib/src/english/ResEng.gf

@@ -523,5 +523,6 @@ resource ResEng = ParamX ** open Prelude in {
               }
       } ;
 
+  finalComma : Str = pre {"," | "." => []; "" => ","; _ => []} ;
 
 }