LOWER leaves letters above U+FFFF alone, and a combining mark stops the final sigma

FN-LOWER-001: LOWER leaves letters above U+FFFF alone, and a combining mark stops the final sigma

Quirk · measured · recorded 2026-11-04

LOWER did not change the Deseret capital U+10400, a cased letter above U+FFFF, either alone or inside other text: LOWER("A𐐀Σ") is "a𐐀ς", where the Greek capital sigma at the end becomes the final form. Greek sigma depends on what follows: followed by a full stop it takes the final form ς, and followed by a combining mark, U+0300 or U+0301, it takes the medial form σ. PROPER treats a character above U+FFFF as a word boundary, so PROPER("a𐐀b") is "A𐐀B", with the B capitalised and the Deseret letter unchanged.

Basis: 6 recorded LOWER and 4 recorded PROPER readings, in a workbook at compatibility version 2.

Inferred: The readings cover one Deseret letter and two combining marks. That every letter above U+FFFF and every mark behave the same is inferred.

Open: Behaviour at compatibility version 1 has not been read for these inputs.