Terseness at different levels. Avoiding boilerplate syntax is good. Obscure abbreviated names of functions and operators just to save a few keystrokes is bad.

Btw. the definition of terseness in the essay seem specifically chosen to favor Lisp style languages.

2 + 3 * 4

is clearly terser than

(+ 2 (* 3 4))

But by counting "leafs" like he does (rather than say tokens), they get the same terseness-count.