Ty. Sorry it was a grumpy warning :(

From memory, it felt like the electrostatic discharge that used to happen whenever I was touching my car.

That's likely a valid comparison. Some parts of the tube might give you the same style of event as static electricity discharge when you touch them. Other parts would give you something more though :D so please don't take this as a generalisation.

Interestingly, the PC suffered no damage at all and didn’t blow its internal fuse, either.

Fuses are OK as fire prevention devices, but mostly useless as electrocution prevention. They blow based off power draw and time. Many human-electric interactions don't actually draw that much power or last that long when compared to normal circuit power draws & timescales.