In typography, rivers (or rivers of white) are gaps in typesetting which appear to run through a paragraph of text due to a coincidental alignment of spaces. Rivers can occur regardless of the spacing settings, but are most noticeable with wide inter-word spaces caused by full text justification or monospaced fonts. Rivers are less noticeable with proportional fonts, due to narrow spacing. Another cause of rivers is the close repetition of a long word or similar words at regular intervals, such as "maximization" with "minimization" or "optimization".
The copywriters in my company stare at a landing page for hours and fix little word flow details.
I remember having to explain responsive design, since words can break on screen size. The old editors who worked on magazines were kind of annoyed. But fortunately, we have better css tools like clamp, and word break to control word flow. But honestly its easier to teach the copywriter how tech works.