I don't see that as a code-bug but a difference in implied requirements. Namely, the expectation about which person can/should choose the width of the lines everyone had to read.

Let's flip it around: Suppose someone put in code/markup to prevent any viewer from picking a larger or smaller font-size. Would that be "just fixing a bug", or would some of us be pissed that the author has dictated something in a way which infringes on our autonomy and disrespects our superior-knowledge about what constitutes our good reading experience?