Caveat:
I don't use the nodeJS server setup, so most of what I say below is just a guess...
Nearly every activity in TiddlyWiki has some effect on one or more underlying system tiddlers, used to track the current "state" of the interface. For example, whenever you view or edit a tiddler, the "list" field in $:/StoryList is updated.
When using nodeJS, all tiddler changes are synced to the corresponding .tid files stored on your server. Then, because those .tid files have been updated, they are being pushed to any other users that are connected to the same nodeJS server.
To work around this, try disabling the default "Autosave" setting to prevent your activities from being actively synced to the server. To turn off this setting, go to $:/ControlPanel, Saving, General tab and choose "Do not save changes automatically".
If this works, then nothing you change in your instance of TiddlyWiki will be written to the server until you use the "Save changes" button in the Sidebar.
Let me know how it goes...
-e