Pages breaking words and punctuation across lines

I created a Pages template using text boxes to control the placement of text on all pages. I discovered when pasting text into those text boxes, Pages indiscriminately breaks words and punctuation across lines of the text box. How can I prevent this behavior?

Hyphenation is disabled. The breaks in Pages are not adding hypens.

I am pasting plain text, so I am certain this is not a source-formatting issue. Interestingly, if I paste rich text, the issue is not present.

The document language is English.