In this particular case, the ea-nasir tablet is pretty popular online and you are one of the lucky 10000 (to use one of the better xkcd memes). But I agree that xkcd tends to be really smug, which makes their worse comics really unpalatable. They are not even being particularly smart, they just use strawmen and big words liberally.

There's actually a pretty large ea-nasir meme-posting culture, it's one of my favourite internet things.

Basically it originated from this cuneiform tablet from 1750BC, the oldest known written complaint.

Translation of the complaint: (source: 1967 Book "Letters from Mesopotamia"

Tell Ea-nasir: Nanni sends the following message:

When you came, you said to me as follows : "I will give Gimil-Sin (when he comes) fine quality copper ingots." You left then but you did not do what you promised me. You put ingots which were not good before my messenger (Sit-Sin) and said: "If you want to take them, take them; if you do not want to take them, go away!"

What do you take me for, that you treat somebody like me with such contempt? I have sent as messengers gentlemen like ourselves to collect the bag with my money (deposited with you) but you have treated me with contempt by sending them back to me empty-handed several times, and that through enemy territory. Is there anyone among the merchants who trade with Telmun who has treated me in this way? You alone treat my messenger with contempt! On account of that one (trifling) mina of silver which I owe(?) you, you feel free to speak in such a way, while I have given to the palace on your behalf 1,080 pounds of copper, and umi-abum has likewise given 1,080 pounds of copper, apart from what we both have had written on a sealed tablet to be kept in the temple of Samas.

How have you treated me for that copper? You have withheld my money bag from me in enemy territory; it is now up to you to restore (my money) to me in full.

Take cognizance that (from now on) I will not accept here any copper from you that is not of fine quality. I shall (from now on) select and take the ingots individually in my own yard, and I shall exercise against you my right of rejection because you have treated me with contempt.

Most of the humour of the various memes and jokes (some examples found here) seems to stem from the fact that Nanni's salt and rage has endured thousands of years and now we know about it. Ea-Nasir will always be remembered as a shitty copper merchant, and there's just something inherently hilarious about that, to me.