Oh dear, I fear that this is going round and round and round in circles a bit, and that no-one else is following it, but here goes anyway :>
The "traversable" permission would be an additional requirement to view any object. Its main purpose would be to distinguish between "use via Web" and "use in DTML only". "standard_html_*" would be usable in DTML but could not be viewed via the web. They would not give "traversable" permission to Anonymous. Many DTML objects, however, would need to give the "traversable" permission even to Anonymous in order to be useful.
OK, I think we're talking about the same thing now...but could you give me an example of any object that would need to be traversable by Anonymous? index_html, for example, doesn't need to be traversable (I still prefer 'listable'). Viewable TTW, yes, but that's all. seb.