twentytenをベースにテーマをカスタマイズしています。 で、テーマを切り替えるときにテーマの情報が表示されるわけですが、あれはどこで定義しているのかしら？と調べたら style.cssの冒頭に記述があるんですね。ここの記述を書き換えて無事最適化すことができました。

/*
Theme Name: Twenty Eleven
Theme URI: http://wordpress.org/extend/themes/twentyeleven
Author: the WordPress team
Author URI: http://wordpress.org/
Description: The 2011 theme for WordPress is sophisticated, lightweight, and adaptable. Make it yours with a custom menu, header image, and background -- then go further with available theme options for light or dark color scheme, custom link colors, and three layout choices. Twenty Eleven comes equipped with a Showcase page template that transforms your front page into a showcase to show off your best content, widget support galore (sidebar, three footer areas, and a Showcase page widget area), and a custom "Ephemera" widget to display your Aside, Link, Quote, or Status posts. Included are styles for print and for the admin editor, support for featured images (as custom header images on posts and pages and as large images on featured "sticky" posts), and special styles for six different post formats.
Version: 1.4
License: GNU General Public License v2 or later
License URI: http://www.gnu.org/licenses/gpl-2.0.html
Tags: dark, light, white, black, gray, one-column, two-columns, left-sidebar, right-sidebar, fixed-width, flexible-width, custom-background, custom-colors, custom-header, custom-menu, editor-style, featured-image-header, featured-images, full-width-template, microformats, post-formats, rtl-language-support, sticky-post, theme-options, translation-ready
Text Domain: twentyeleven
*/

WordPressはたまにしかいじらないこともあり、備忘録に書き忘れるとまた1から調べて対応するはめになってしまうので、些細なことでも記録しておこうと思います。