[alkonaut]

> The OP thinks that humans read thinner columns faster.

Tbf, "reading faster" in the linear sense is probably not exactly the metric to use when writing text. When writing, I usually need to jump randomly a lot in the text to cross reference something (from the last paragraph, the last sentence, or the beginning of the current sentence). It's a kind of nonlinear scanning that I'm guessing could be more efficient in narrow column text, even if wider columns would be faster to read from beginning to end.