General
• WordPress.com themes – from oldest to newest
• WordPress.com themes – from most to least popular

Various features
• Archives and Links page templates
• Blockquote style
• Category/archive pages: full posts or not
• Category descriptions
• Child pages: links displayed on parent or as dropdowns
• Color customisable themes
• Comments: allowed HTML (1)
• The Excerpt function
• Gallery attachment pages: navigation links and image links
• The Gallery format as custom excerpt
• Featured images
• Alternative post formats
• The 404 error message
• Header images
• Position absolute (pt. 2)
• Sidebars and other widget areas: number and position
• Sticky posts and their appearance
Including list of themes that support
a) alert/intro/notice box, b) featured posts slider.
• Widgets on static pages or single posts
• Non widget-aware themes
Post obsolete: all themes are now widget enabled.

Widths
• Maximum displayed image width
• Sidebar width

Fonts
• Default theme fonts
• Main text font size compared
• Themes with serif fonts

Various tabs
• Author and profile displayed or not
• Category pages: heading or no heading
• The comments tab
• Comments Off (1)
Tabs/messages on main page & category/archive pages.
• Comments Off (2)
Tabs/messages on single posts & static pages.
• Date on static pages
• Header tabs
• The Home tab
• Page tabs as extra links
• Previous/next navigation links (1)
On main & category/archive pages.
• Previous/next navigation links (2)
On single posts.
• RSS and social media icons
• Tagline or no tagline
• Posting time displayed or not