Index: src/net/sourceforge/kolmafia/preferences/Preferences.java
===================================================================
--- src/net/sourceforge/kolmafia/preferences/Preferences.java	(revision 12105)
+++ src/net/sourceforge/kolmafia/preferences/Preferences.java	(working copy)
@@ -83,6 +83,8 @@
 	private static final HashMap globalNames = new HashMap();
 	private static final TreeMap globalValues = new TreeMap();
 	private static File globalPropertiesFile = null;
+	
+	private static final TreeMap defaultsMap = new TreeMap();
 
 	static
 	{
@@ -601,6 +603,9 @@
 				String value = current.length == 2 ? "" : current[ 2 ];
 				desiredMap = map.equals( "global" ) ? Preferences.globalNames : Preferences.userNames;
 				desiredMap.put( name, value );
+
+				// Maintain a map of prefs that exist in defaults.txt
+				defaultsMap.put( name, value );
 			}
 		}
 
@@ -744,10 +749,24 @@
 			String name = (String) i.next();
 			if ( name.startsWith( "_" ) )
 			{
+				if ( !Preferences.containsDefault( name ) )
+				{
+					i.remove();
+					if ( Preferences.getBoolean( "saveSettingsOnSet" ) )
+					{
+						Preferences.saveToFile( Preferences.userPropertiesFile, Preferences.userValues );
+					}
+					continue;
+				}
 				String val = (String) Preferences.userNames.get( name );
 				if ( val == null ) val = "";
 				Preferences.setString( name, val );
 			}
 		}
 	}
+
+	public static boolean containsDefault( String key )
+	{
+		return defaultsMap.containsKey( key );
+	}
 }
Index: src/net/sourceforge/kolmafia/textui/command/SetPreferencesCommand.java
===================================================================
--- src/net/sourceforge/kolmafia/textui/command/SetPreferencesCommand.java	(revision 12105)
+++ src/net/sourceforge/kolmafia/textui/command/SetPreferencesCommand.java	(working copy)
@@ -139,7 +139,8 @@
 			return;
 		}
 
-		RequestLogger.printLine( name + " => " + value );
+		if ( !name.startsWith( "_" ) || Preferences.containsDefault( name ) )
+			RequestLogger.printLine( name + " => " + value );
 		Preferences.setString( name, value );
 
 		if ( name.startsWith( "combatHotkey" ) )