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I suppose it each to there own when going over and above spec. Your right with considering nuisance tripping with the increased earth leakage from electronics.
I have no issue with going over and above to improve a situation if it is genuinely well thought out and actually improves a situation. However you have not presented this as a way of going over and above, you presented it as good practice, this implies that the industry as a whole approves of it rather than being your personal opinion.
I still fail to see the point of installing an extra 100mA RCD on a normal TN installation.
A 100mA RCD does not provide additional protection, it will allow a fatal electric shock before it operates so does not provide any back-up to a 30mA RCD. It may however provide a false sense of security for someone who doesn't understand this.
For earth fault protection you already have multiple means of detecting those faults either by MCB and 30mA RCD or 30mA RCBO.
Nuisance tripping will occur with neutral to earth faults because RCBO's (assuming they are used) generally do not disconnect the neutral, so the 100mA RCD will trip as well as the 30mA RCBO. This will defeat the whole object of dividing the installation up across multiple RCDs. Again, in my opinion, it gives a false sense of security whilst having the potential to create a larger problem.