functions_display.php defines the following template variable for the forumrow block which fails to obtain the appropriate language value from the $user->lang array. The returned value is simply the array key. Bantu suggested removing it as FORUM_FOLDER_IMG_ALT performs the same function correctly.
viewtopic.php defines the following template variable which uses the SEARCH_USER_POSTS lang key as alt text. The key is defined in language/en/memberlist.php, so the actual language value is never returned.