A wiki should be an oasis of taft.
Pages should be small, despite my "wiki is not a dictionary" principle. The focus should be on the graph as content. Concepts should be reified into nodes in the graph, and their place within the set of links should be just as important as the content.
The site should be woven through a similar principle to Ghyll, where every page must have a certain number of inbound and outbound links.
Editing should be done through Markdown. Editing source is easier than using a GUI, where you have to remember arbitrary chording sequences. Memorising the slight syntax of Markdown is much easier.
Pages should be made from blocks. A block can be a heading, paragraph, preformatted section, etc. Each block should be saved permanently, using unixtime and SHA-256 hash. Pages are then built from sequences of blocks.
The browser should allow you to edit each block, and also to rearrange, delete and add blocks. There should also be a way to manage the graph topology.
Question: should pages be saved as blocks? Sounds reasonable. So there would be two block types: Markdown content blocks, and super-blocks that contain only references to other blocks.
Allowing nesting of super-blocks to form sections may be useful, but should be permitted for one level only.
Page, or concept, names should follow Wikipedia style.