Haven't seen a definitive explanation but it's drinking your first sip (gulp) down to either in between the harp and the text or to the middle of the "G"
Rather than say, just f***ing drinking your drink like a normal person
Unfortunately it's the price we pay for loving an aesthetically pleasing drink.
Guinness is absolutely all over social media especially since the whole "splitting the g" nonsense took off
I love Guinness and Murphy's- do find it hard to get into other Stouts really and find a lot of them either too sweet or too strong (or both)
I do enjoy Camden Stout though- they've got it at Worthing FC