I noticed that, in WordPress ME, the post_modified field in the _wp_posts table is not used at all. I thought it would normally be correct to put NOW() into that field whenever an article is written or updated, so I went ahead and tried patching it myself.
$ !diff
diff post.php.orig post.php
118c118
< (ID, post_author, post_date, post_content, post_title, post_lat, post_lon, post_excerpt, post_status, comment_status, ping_status, post_password, post_name, to_ping) --- > (ID, post_author, post_date, post_content, post_title, post_lat, post_lon, post_excerpt, post_status, comment_status, ping_status, post_password, post_name, to_ping, post_modified)
120c120
< (\\'0\\', \\'$user_ID\\', \\'$now\\', \\'$content\\', \\'$post_title\\', $post_latf, $post_lonf,\\'$excerpt\\', \\'$post_status\\', \\'$comment_status\\', \\'$ping_status\\', \\'$post_password\\', \\'$post_name\\', \\'$trackback\\') --- > (\\’0\\’, \\’$user_ID\\’, \\’$now\\’, \\’$content\\’, \\’$post_title\\’, $post_latf, $post_lonf,\\’$excerpt\\’, \\’$post_status\\’, \\’$comment_status\\’, \\’$ping_status\\’, \\’$post_password\\’, \\’$post_name\\’, \\’$trackback\\’, NOW() )
124c124
< (ID, post_author, post_date, post_content, post_title, post_excerpt, post_status, comment_status, ping_status, post_password, post_name, to_ping) --- > (ID, post_author, post_date, post_content, post_title, post_excerpt, post_status, comment_status, ping_status, post_password, post_name, to_ping, post_modified)
126c126
< (\\'0\\', \\'$user_ID\\', \\'$now\\', \\'$content\\', \\'$post_title\\', \\'$excerpt\\', \\'$post_status\\', \\'$comment_status\\', \\'$ping_status\\', \\'$post_password\\', \\'$post_name\\', \\'$trackback\\') --- > (\\’0\\’, \\’$user_ID\\’, \\’$now\\’, \\’$content\\’, \\’$post_title\\’, \\’$excerpt\\’, \\’$post_status\\’, \\’$comment_status\\’, \\’$ping_status\\’, \\’$post_password\\’, \\’$post_name\\’, \\’$trackback\\’, NOW())
321a322
> post_modified = NOW(),
What do you think?