When any IDEOGRAPHIC SPACEs (U+3000) are included in anchor of wikiLinks,
they are replaced with SPACEs (and then LOW LINEs) in URL anchors.
But in section anchors of article bodies, they are not replaced.
As a result, wikiLinks with anchor including IDEOGRAPHIC SPACE(s) are "broken".
IDEOGRAPHIC SPACE in anchor should be either always normalized or always not.
Original reports at ja.Wikipedia ([[w:ja:WP:BUG]]):