Index: trunk/src/org/openstreetmap/josm/actions/ShowStatusReportAction.java
===================================================================
--- trunk/src/org/openstreetmap/josm/actions/ShowStatusReportAction.java	(revision 17816)
+++ trunk/src/org/openstreetmap/josm/actions/ShowStatusReportAction.java	(revision 17820)
@@ -96,5 +96,5 @@
             text.format("OS Build number: %s%n", buildNumber);
         }
-        text.format("Memory Usage: %d MB / %d MB (%d MB allocated, but free)%n",
+        text.format(Locale.ROOT, "Memory Usage: %d MB / %d MB (%d MB allocated, but free)%n",
                 Runtime.getRuntime().totalMemory() / 1024 / 1024,
                 Runtime.getRuntime().maxMemory() / 1024 / 1024,
@@ -114,5 +114,5 @@
                     AffineTransform transform = gd.getDefaultConfiguration().getDefaultTransform();
                     // Java 11: use DisplayMode#toString
-                    text.format(" %d\u00D7%d (scaling %.2f\u00D7%.2f)",
+                    text.format(Locale.ROOT, " %d\u00D7%d (scaling %.2f\u00D7%.2f)",
                             dm.getWidth(), dm.getHeight(), transform.getScaleX(), transform.getScaleY());
                 }
@@ -141,4 +141,6 @@
             }
         }
+        text.format("Locale info: %s%n", Locale.getDefault().toString());
+        text.format("Numbers with default locale: %s -> %d%n", Integer.toString(1_234_567_890), 1_234_567_890);
 
         if (PlatformManager.isPlatformUnixoid()) {
Index: trunk/src/org/openstreetmap/josm/tools/Logging.java
===================================================================
--- trunk/src/org/openstreetmap/josm/tools/Logging.java	(revision 17816)
+++ trunk/src/org/openstreetmap/josm/tools/Logging.java	(revision 17820)
@@ -12,4 +12,5 @@
 import java.util.Arrays;
 import java.util.List;
+import java.util.Locale;
 import java.util.function.Supplier;
 import java.util.logging.ConsoleHandler;
@@ -496,5 +497,5 @@
             }
 
-            String msg = String.format("%09.3f %s%s", startup.elapsed() / 1000., getPrefix(record), record.getMessage());
+            String msg = String.format(Locale.ROOT, "%09.3f %s%s", startup.elapsed() / 1000., getPrefix(record), record.getMessage());
 
             // Only remember first line of message