Simply, when someone disagrees with a change to the page. For example, coolpup and I have different styles - which are sometimes incompatible. Going to be working on the Style Guide and Template - so input from everyone would be handy.

On wikipedia when people want conflicting changes a discussion between all interested parties is setup - this usually finds a resolution. also wikipedia has definite guidelines for different article/page types.

To be honest I find if an experienced person edits a page or regularly edits that page, then it is up to them to style it . . .
If you apply a style to every page on the wiki that is fine with me
For example the [[HomePage]] > [[SoftwareIndex Software Index]] > [[SoftwareNetwork Network]] that you have implemented is a good idea :)