Add layout container

Many layout techniques require an overall page container.
Separate content and comments
Keep metadata in header
Basic outline and semantics working on base, post, index, and tags

Readability; IE 11, Safari, and Firefox’s reading modes supported.
Use post.author()
Lists

Tag.tmpl still duplicates parts of list_post.tmpl.
breadcrumbs are navigational elements
Stories are a lot like posts