I deliberately created this tiddler with '[[' and ']]' using the create a new tiddler function. However, I am pretty sure that extraclusion can also create tanks in this form because I have have found some tiddlers in one of my tanks that have names in this form and since they have long names with embedded spaced I am fairly certain that they were created in some experiments with extraclusion. I am not sure that it should be allowed - if only because it could have cause difficulties long term. I haven't tried other characters.