As I've said, it is only relevant to safety in the hands of less-than-fully-competent electricians. In fact, the ultimate in 'safety' might be to completely do away with colour-identification of conductors, thereby forcing electricians to find out for themselves which conductor was being used for which purpose!Clearly it's a safety requirement, irrespective of individual views of the need for or wisdom of the Rule.
In any event, as EFLI has observed, no amount of 'rules' about identification of conductors can guarantee that all electricians will always connect things correctly.
Even if you asked every electrician in the (any) country, I think you might struggle to find examples of 'safety issues' that had arisen because of terminal over-sleeving of conductors, and I find it hard to believe that electricians in ROI are any less competent, or any more likely to 'make mistakes' than are their counterparts in other countries - so I have to wonder whether there really is any sensible evidence-base foor this 'rule'?

