Those provisions do not affect the clear and straightforward requirement of 514.4.2. ... "The bi-colour combination green-and-yellow shall be used exclusively for identification of a protective conductor and this combination shall not be used for any other purpose."
I think we'll probably have to agree to disagree on this one.
It's all a question of what BS 7671 regards as "used for identification". My interpretation is that, as far as 'identification' is concerned, over-sleeving over-rides native insulation colour. Hence, when the terminations of a blue-insulated conductor is over-sleeved with brown, then that satisfactorily identifies it as a live conductor - in other words, it is the brown sleeving, not the underlying blue insulation which is being "used for identification".
If you accept that (which maybe you don't) then, by analogy, if one overs-sleeves a G/Y-insulated conductor with brown sleeving, it is the brown sleeving, not the underlying G/Y insulation, which is being "used for identification" - so G/Y is not being "used for identification" of something which is not a protective conductor (which, if it were, would be in violation of 514.4.2).
As above, we're probably not going to agree about this - but, FWIW, I know that I am not the only person to interpret the regs in this way. None of this alters the fact that, as I've said, I would personally not over-sleeve a G/Y, and would not regard that as 'good practice'.
Kind Regards, John