Similar in spirit to replies on TiddlySpace but with a name that is less implying of 'threads". Also easier to implement because of lack of domain restrictions.
The idea is that if you see a tiddler you find interesting you can make a twin of it in your own "home" tank. It will be tagged with the current tank and the username of the modifier and will link to the original.
This is driven largely by seeing a fair few tiddlers in the last few days that I want to react to.
Another option would be comments, but they are less KnowledgeNetwork building.