An essay by Cecelia Watson, in the Paris Review: “The Birth of the Semicolon.”

The semicolon was born in Venice in 1494. It was meant to signify a pause of a length somewhere between that of the comma and that of the colon, and this heritage was reflected in its form, which combines half of each of those marks. It was born into a time period of writerly experimentation and invention, a time when there were no punctuation rules, and readers created and discarded novel punctuation marks regularly.

[…]

The Bembo typeface’s tall semicolon was the original that appeared in De Aetna, with its comma-half tensely coiled, tail thorn-sharp beneath the perfect orb thrown high above it. The semicolon in Poliphilus, relaxed and fuzzy, looks casual in comparison, like a Keith Haring character taking a break from buzzing. Garamond’s semicolon is watchful, aggressive, and elegant, its lower half a cobra’s head arced back to strike. Jenson’s is a simple shooting star.

And from the Guardian, an interview with Gretchen McCulloch that takes up the comma ellipsis and more:

Gretchen McCulloch is an internet linguist who analyses the ways we communicate online. Her debut book Because Internet: Understanding the New Rules of Language explores the acronyms, memes, punctuation, and emoji that make up our modern discourse.