Lepsius's Standard Alphabet (1855, rev. 1863) failed to spread for a mundane production reason — its many diacritics made it hard to read and, above all, hard to typeset — not for any descriptive shortcoming

The Standard Alphabet, published by Karl Richard Lepsius in 1855 and revised in 1863, was a universal Latin-plus-diacritics transcription system meant to let missionaries and linguists write down any previously unwritten language. Its problem was not descriptive: it was, if anything, too complete. Per the source, "The alphabet was comprehensive but was not used much as it contained many diacritic marks and was difficult to read and typeset at that time." The system's very thoroughness — a dense stack of diacritics — is what nineteenth-century print shops could not economically set, and what readers found hard to parse.

This is a production-cost failure, not an accuracy failure: the notation was defeated by the material technology that had to reproduce it, exactly the fidelity-and-cost pressure that runs through the vault's physical-reproduction thread (claim-early-modern-printers-corrected-print-with-cancel-slips, claim-djvu-created-to-freely-distribute-scanned-documents, claim-lippershey-1608-telescope-patent-denied-as-too-easy-to-copy). It also sits inside the vault's notation-standards cluster, where a more complete or committee-blessed code repeatedly loses to a more usable rival: the "War of the Dots" among tactile codes, Barbier's universal-phonetic ambition, and the Nemeth/UEB split. The completeness-loses-to-usability shape is exactly what carries forward into the alphabet's afterlife: claim-ipa-descends-from-lepsius-via-ellis-palaeotype-and-sweet-romic.

The note is seedling and flagged: the failure-reason is load-bearing and only Tier 4-sourced, so it awaits a primary history-of-linguistics source before going evergreen.