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....
Note that Han Unification has a history predating Unicode, and the Unicode work very much followed on from that.
The most notable is CCCII, developed in Taiwan in the early 80s, and then standardised in various places.
That's not to say that it hasn't been controversial (it has!), nor to say that it hasn't caused problems (it has!), but it's also unfair to say that it's just Unicode doing its own special thing.
What is the rationale to the unifying direction of changes in Unicode?
The Han unification probably was about fitting CJK into the 16 bits aka BMP. It was a blunder indeed.
> apparently the Japanese did not like Unicode's tendencies towards Aristotelian essentialism
Do you mean Han Unification? I.e. that conceptually equivalent characters which are written differently in Japan and China received only a single unicode code-point, and are rendered the Chinese way by default on most computers?