Why Simplifying a Sentence Made the Readability Score Worse
This can happen when splitting a longer sentence into two shorter ones inadvertently introduces more polysyllabic words per sentence (raising average word complexity per sentence), or when a simplification replaces a common short word with a technically simpler-sounding but actually longer or less familiar word — since the formula measures structural word and sentence length specifically, not genuine plain-language familiarity.
This counterintuitive result is a direct consequence of what the formula actually measures (covered in the score-meaning guide), not a flaw in the concept of simplification itself.
A worked illustration
Splitting a single 20-word sentence into two 10-word sentences generally improves the score, since shorter average sentence length is usually favorable — but if the split requires adding transitional words or restructuring that happens to introduce a few more multi-syllable words, the word-complexity component of the score can offset or even outweigh the sentence-length improvement.
Why word choice matters as much as sentence structure
A formula measuring syllables per word doesn't distinguish between a long, unfamiliar technical word and a long but very commonly understood word — an edit that shortens sentences but happens to introduce a less common longer word can worsen the calculated score even though the edit was genuinely intended to simplify.
What this reveals about relying purely on the score
This specific scenario is a clear, concrete illustration of the limitation covered in the score-meaning guide — the formula can't distinguish a genuinely clarifying edit from one that happens to shift the specific structural inputs it measures, which is why the score should inform, not solely dictate, editing decisions.