Index: /applications/editors/josm/plugins/reverter/src/reverter/ReverterUploadHook.java
===================================================================
--- /applications/editors/josm/plugins/reverter/src/reverter/ReverterUploadHook.java	(revision 35998)
+++ /applications/editors/josm/plugins/reverter/src/reverter/ReverterUploadHook.java	(revision 35999)
@@ -32,5 +32,5 @@
             for (Command cmd : UndoRedoHandler.getInstance().getUndoCommands()) {
                 if (Objects.equals(MainApplication.getLayerManager().getEditDataSet(), cmd.getAffectedDataSet()) && isReverterCmd(cmd)) {
-                    tags.put("created_by", pluginString);
+                    tags.merge("created_by", pluginString, (oldValue, value) -> String.join(";", value, oldValue));
                     break;
                 }