The article links to the Nico Nico Douga Wiki (a wiki for creative works), in which each of the 12 characters is imagined to be the name of a Japanese youkai (a type of spirit/demon/monster): http://dic.nicovideo.jp/a/%E5%B9%BD%E9%9C%8A%E6%96%87%E5%AD%... (Japanese). It’s also quite a neat coincidence that there are exactly 12 remaining unattested characters (down from ~60 before the thorough investigation), because 12 is a rather auspicious number in East Asian tradition.

For example, 妛 (山 mountain atop 女 female) is imagined to mean a yama-uba (traditional “mountain witch” youkai) who lives at the foot of the mountain (as befitting the “女” position in the character).

There’s a good tradition of reusing old or outdated characters in new contexts. For example, in Chinese, the archaic character 囧, meaning “window” (modern term 窗) has been resurrected to mean “embarrassed” or “awkward” due to its pictorial resemblance to a facial expression.