Remove box character after excerpts. Special Character Bug

You’ll want to use the excerpt_more filter to modify this text. e.g.:

function mytheme_filter_excerpt_more( $more ) {
    return $more="[read more]";
}
add_filter( 'excerpt_more', 'mytheme_filter_excerpt_more' );

You’ll also want to make sure that nothing else is applying this filter, as it may be the cause of your problem. (If not that, then there is probably an issue with the character encoding, or internationalization/translation strings, etc. for your Theme.)