Is it possible to remove it in the RSS feed itself ?
RSS reader will display the description as is. The plugin has no idea about the text.
Other suggestion I can think of is in feed.php search for below line
$desc = str_replace( array( "\n", "\r" ), ' ', esc_attr( strip_tags( @html_entity_decode( $item->get_description(), ENT_QUOTES, get_option('blog_charset') ) ) ) );
and replace it with below
$desc = str_replace( array( "\n", "\r" ), ' ', esc_attr( strip_tags( @html_entity_decode( $item->get_description(), ENT_QUOTES, get_option('blog_charset') ), '<span>' ) ) );
Then use the CSS .informations{display: none}
Thanks,
Aakash