Did you know that there’s a WordPress.com-specific version of Underscores?
By adding a special parameter, your download will include special code used only in themes on WordPress.com. Use it to make the greatest theme ever, and send it in to themes [at] automattic.com for consideration!
http://underscores.me/?can_i_haz_wpcom
ThemeShaper 
This link: http://underscores.me/?can_i_haz_wpcom send me to http://underscores.me.
What’s the special parameter to add to _S to make it work in wp.com???
When that parameter is in your URL while on underscores.me, the additional WP.com code will be included in the theme you generate. If the parameter isn’t there, the generated theme won’t include the WP.com file.
Gracias! time to work on it.
Would you prefer anything people might send in to have been reviewed for the wordpress.org theme directory already?
No, it doesn’t have to be in the .org repo, but our review process and standards are very similar.