diff --git a/roles/mongodb/defaults/main.yml b/roles/mongodb/defaults/main.yml
index e1269e9d8..a96fe6f99 100644
--- a/roles/mongodb/defaults/main.yml
+++ b/roles/mongodb/defaults/main.yml
@@ -1,4 +1,18 @@
-# mongodb_install: False
+# MongoDB (/library/dbdata/mongodb) greatly enhances the Sugarizer experience.
+# The roles/mongodb playbook (was?) invoked by roles/sugarizer/meta/main.yml
+
+# 2020-01-23: mongodb_install is completely ignored as MongoDB is installed on
+# demand as a dependency -- by Sugarizer -- but for now we set fake value
+# 'mongodb_install: True' for 'mongodb_installed is defined' tests e.g. in
+# 0-init/tasks/validate_vars.yml
+
+# mongodb_install: True
+
+# FYI 'mongodb_enabled: False' works when Sugarizer is disabled.  Required by
+# mongodb/tasks/enable.yml to shut down the service and log status, but that is
+# misleading as Sugarizer starts mongodb's systemd service on its own, due to
+# 'Requires=mongodb.service' within /etc/systemd/system/sugarizer.service
+
 # mongodb_enabled: False
 
 # mongodb_port: 27018