This is a fascinating thread which raises the question 'Who did the annotations and why?'.
It is understandable that, as the 1939 Register was used as the basis for Ration Books, it would be worth while continuing to update it through to the mid 1950's. But to 1990?
I guess the work was done by or in conjunction with GRO and funded by the taxpayer. Bearing in mid the Register was not digitized, this must have been a major task and presumably, someone thought it was worthwhile keeping tabs on people all this while. Sounds a bit Big Brother-ish to me.
Having said that, the annotated notes have been a help to me in identifying relatives.