Improve comments, as request in code review.

Author: dpvc

ts/input/tex/base/BaseConfiguration.ts

@@ -98,23 +98,32 @@ function envUndefined(_parser: TexParser, env: string) {
 function filterNonscript({data}: {data: ParseOptions}) {
   for (const mml of data.getList('nonscript')) {
     //
-    //  If we are in script or script-script style
-    //    remove the space (either mspace or mrow containing it)
-    //    and remove it (and its contents) from the other lists.
-    //  Otherwise, if it is an mrow (which we added),
-    //    replace the mrow with its contents
-    //    and remove it from its list
+    //  This is the list of mspace elements or mrow > mstyle > mspace
+    //    that followed \nonscript macros to be tested for removal.
     //
     if (mml.attributes.get('scriptlevel') > 0) {
+      //
+      //  The mspace needs to be removed, since we are in a script style.
+      //  Remove it from the DOM and from the list of mspace elements.
+      //
       const parent = mml.parent;
       parent.childNodes.splice(parent.childIndex(mml), 1);
       data.removeFromList(mml.kind, [mml]);
+      //
+      //  If it is an mrow > mstyle > mspace, then we have just
+      //    removed the mrow from its list, and must remove
+      //    the mstyle and mspace from their lists as well.
+      //
       if (mml.isKind('mrow')) {
         const mstyle = mml.childNodes[0] as MmlNode;
         data.removeFromList('mstyle', [mstyle]);
         data.removeFromList('mspace', mstyle.childNodes[0].childNodes as MmlNode[]);
       }
     } else if (mml.isKind('mrow')) {
+      //
+      // This is an mrow > mstyle > mspace  but we're not in a script
+      //   style, so remove the mrow that we had added in the NonscriptItem.
+      //
       mml.parent.replaceChild(mml.childNodes[0], mml);
       data.removeFromList('mrow', [mml]);
     }

ts/input/tex/base/BaseItems.ts

@@ -774,6 +774,9 @@ export class NotItem extends BaseItem {
   }
 }
 
+/**
+ * A StackItem that removes an mspace that follows it (for \nonscript).
+ */
 export class NonscriptItem extends BaseItem {
 
   /**
@@ -787,25 +790,30 @@ export class NonscriptItem extends BaseItem {
    * @override
    */
   public checkItem(item: StackItem): CheckType {
+    //
+    //  Check if the next item is an mspace (or an mspace in an mstyle) and remove it.
+    //
     if (item.isKind('mml') && item.Size() === 1) {
       let mml = item.First;
       //
-      //  Space macros like \, wrap with an mstyle to set scriptlevel=0 (so size is independent of level)
+      //  Space macros like \, are wrapped with an mstyle to set scriptlevel="0"
+      //    (so size is independent of level), we look at the contents of the mstyle for the mspace.
       //
       if (mml.isKind('mstyle') && mml.notParent) {
         mml = NodeUtil.getChildren(NodeUtil.getChildren(mml)[0])[0];
       }
       if (mml.isKind('mspace')) {
         //
-        //  If the space is in an mstyle, wrap it in an mrow so we can test is scriptlevel.
-        //  The mrow will be removed in the post-filter.
+        //  If the space is in an mstyle, wrap it in an mrow so we can test its scriptlevel
+        //    in the post-filter (the mrow will be removed in the filter).  We can't test
+        //    the mstyle's scriptlevel, since it is ecxplicitly setting it to 0.
         //
         if (mml !== item.First) {
-          mml = this.create('node', 'mrow', [item.Pop()]);
-          item.Push(mml);
+          const mrow = this.create('node', 'mrow', [item.Pop()]);
+          item.Push(mrow);
         }
         //
-        //  Save the item for alter post-processing
+        //  Save the mspace for later post-processing.
         //
         this.factory.configuration.addNode('nonscript', item.First);
       }