BPE Morpheme-Length Clustering Across 55 Writing System Corpora: Typological Validation, Voynich Discriminant Zone, and Six Extended Analyses

Paper 6 (Silva 2026) introduced BPE Mean Vocabulary Morpheme Length (VMML) as a writing system classifier and showed that the Voynich Manuscript occupies a discriminant zone (VMML = 5.918, 95% CI 5.77-6.05) above all 15 tested alphabetic natural languages. This paper (v2.0) expands to 55 corpora across 30+ languages and reports six extended analyses: (1) Alphabetic ceiling confirmed at 5.76; (2) Tagalog (VMML=5.914) is the sole natural-language entry into the Voynich CI, but BC=0.202 distinguishes it from Voynich (BC=0.361); (3) Romanization inflates VMML by 2.4-5.3 units (methodological confound). Extended analyses: (4) Currier A vs B: delta VMML=+1.27, delta CBMI=+0.16 bits -- two quantifiably distinct writing registers; (5) BC coherent across all 7 manuscript sections (CV=6.7%) -- single writing system confirmed; (6) 3D discriminant (VMML x BC x CBMI): Voynich isolated, nearest natural-language neighbor Irish at distance 0.17; (7) Six named hoax mechanisms (monoalphabetic, Vigenere/barbavara, Vigenere/Italian-Knowles 2026, null insertion, syllabic compression, vocabulary shuffle) each fail all three criteria simultaneously; (8) BC orthogonal to all classical textual metrics (|r| < 0.23 vs entropy, TTR, hapax, Zipf) -- genuinely new structural dimension. All code and six extension scripts publicly available in companion repository.