Avestan Sshe and the Measure of a Script's Precision

Four separate letters for the sh region of the sound system is a larger provision than any script of the period made, and it is the fact most often cited when the Avestan alphabet is called phonetically exact. The distinctions come from the recitation, not from the scribes. A script made in the Sasanian period for a text composed a thousand years and more earlier is an act of preservation rather than of composition. Nothing was being written down for the first time. What was being done was the fixing, in a form that would not drift, of something priests already held in memory. The script was put to a second use as well.

Pazand is Middle Persian written in Avestan letters, taken up precisely because those letters record vowels and the Pahlavi ones did not, and it is the clearest practical demonstration of what the alphabet was good for. In the digital record the letter is encoded at U+10B34 AVESTAN LETTER SSHE. The Avestan block sits wholly in the supplementary planes, and every letter in it takes four bytes in the encoding most of the web runs on. That is the practical reason Avestan text is still uncommon online, and why a page carrying it depends on the reader having a font that covers the range. Zoroastrianism is a living religion with a small community, and the Avesta is its liturgy rather than its archive. The letters of this alphabet are therefore not an antiquarian matter. They record sounds a priest is still expected to produce.