Computer safety when jump starting

This started as daydreaming about what I needed to isolate if welding to a vehicle with a computer management system. I called the RAA tech branch and the answer was revealing to say the least!

If welding anything to a vehicle remove all computers and put them on the bench away from any possibilities of voltage spikes. If this is not done the spike may well cook the computer but (wait for it) the computer may not die till later, in some cases months later.
Crash repairers and exhaust fitters don't necessarily know this and blithely mig bits back together and mig exhaust bits on without realising they may be causing expensive problems down the track. When we are crossing the Tanami Desert and the Pooter dies at the worst. (Too horrible to contemplate)
I recall that the computer on a car previously owned by SWAMBO died mysteriously some considerable time after crash repairs. Now maybe we know why.

Now to the guts of my post.
I asked the tech about jump starting. This is fine apparently if from an isolated donor battery as there will be no spikes. But if the donor car has its engine running there is risk of a spike. So if you switch off the motor in the donor car there will be no spike from it to the recipient car. But what about when the recipient car starts (assuming the donor car has a pooter running things) it can presumably send a spike back the other way and damage the computer in the donor car?

Reckon in future I will be less enthusiastic about leaping in to jump-start hapless roadside victims. But if I do feel the good samaritan urge I will be sure to stop my motor and disconnect the battery completely before doing the business.
Jumper leads with so-called spike protection do not live up to their names apparently.

All in the interests of saving unecessary expenditure,
Cheers
Camper