A dirty patch to mongoose that allows a few deep-population queries to work, whilst breaking other things! Don't use it! :D

gistfile1.diff

diff --git a/lib/model.js b/lib/model.js
index 53a21e1..ba76805 100644
--- a/lib/model.js
+++ b/lib/model.js
@@ -1944,6 +1944,13 @@ function populate (model, docs, options, cb) {
     return cb();
   }

+
+  // We may be asked to resolve path "comments._creator" but we are given the comments, so we only need to look into doc["_creator"], so let's drop the first part of the path.  TOOD: Or should this be all but the last part?
+  var seekPath = path;
+  if (path.indexOf(".")>=0) {
+    seekPath = path.split(".").slice(1).join(".");
+  }
+
   var rawIds = [];
   var i, doc, id;
   var len = docs.length;
@@ -1968,7 +1975,7 @@ function populate (model, docs, options, cb) {
     }

     if (!ret || Array.isArray(ret) && 0 === ret.length) {
-      ret = utils.getValue(path, doc);
+      ret = utils.getValue(seekPath, doc);
     }

     if (ret) {
@@ -2261,6 +2269,7 @@ function assignRawDocsToIdStructure (rawIds, resultDocs, resultOrder, options, r
 Model._getSchema = function _getSchema (path) {
   var schema = this.schema
     , pathschema = schema.path(path);
+  var db = this.db;

   if (pathschema)
     return pathschema;
@@ -2287,6 +2296,15 @@ Model._getSchema = function _getSchema (path) {
           // Also we need to handle array.$.path since schema.path
           // doesn't work for that.
           if (p !== parts.length) {
+            if (!foundschema.schema) {
+              var nextModelName = foundschema.caster.options && foundschema.caster.options.ref;
+              if (nextModelName) {
+                console.info("Got (through array) nextModelName="+nextModelName);
+                var nextmodel = db.model(nextModelName);
+                foundschema = nextmodel;
+              }
+            }
             if ('$' === parts[p]) {
               // comments.$.comments.$.title
               return search(parts.slice(p+1), foundschema.schema);