The colon exclusion was preventing legitimate headings like "Steps for Using the Microscope:" and "Changing objectives:" from being detected. The single edge case it was protecting (chart sub-headers) is less impactful than the many headings it was blocking. Benchmark improvement: MHS 0.51→0.52, MHS-S 0.61→0.62. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>