Why do I measure (almost) no voltage between 230V phase and my body?
Mains neutral/earth is tied to the general mass of the earth.

Digital multimeters normally have an input impedance of 10MΩ. So a reading of 8V means that 0.8uA was flowing between the mains and your body through the multimeter.

At the time you made your measurement the impedance between your body and the general mass of the earth was much higher than the input impedance of your multimeter. So most of the voltage was dropped between your body and the general mass of the earth rather than across the multimeter.

It follows that if nothing had changed since you made the measurement and you touched the mains live conductor you would not have recieved a shock.

Of course it is all too easy to end up inadvertantly grounding your body, so I strongly reccomend avoiding touching live mains.