Well, vast swaths of the Kangxi dictionary (which serves as "sources" for probably most of the CJK characters) are such "ghost" characters as described in the article...
The peculiar properties of CJK characters and the philosophy (apparently the Japanese did not like Unicode's tendencies towards Aristotelian essentialism) under which they were implemented in Unicode probably singlehandedly forced unicode to expand beyond the BMP....
The peculiar properties of CJK characters and the philosophy (apparently the Japanese did not like Unicode's tendencies towards Aristotelian essentialism) under which they were implemented in Unicode probably singlehandedly forced unicode to expand beyond the BMP....