You can fix it by switching to one of the grounded charger heads. Unfortunately in most locales those are only available with an integrated extension cable (or as everyone seems to call them, the "gooseneck" cables)

It happens with other 2-pin chargers on both MacBooks and other laptops, but it depends upon various factors how strong the leakage is

They can’t, it’s caused by the capacitors required to suppress electromagnetic interference caused by the switch-mode power supply. These allow a very very tiny amount of current to leak through from the mains side, which is then capacitively coupled to the metal case (IIRC Apple do not connect the case to power negative) reducing it further, but it’s enough for humans to sense it.

It can be avoided by using a grounded power supply, but because there are large countries that have ungrounded outlets in common use the most designs are ungrounded.

It's also an issue on the new Neo. It was the first thing I noticed when I tried one in the Apple Store. I unplugged the power cable and it went away, replugged and it came back. I'm in the UK so I expected grounded electricity supply.

You wouldn't have this if your plug was properly grounded. Most developed countries have plugs that have grounding. EU via side pins UK via third prong