U+FE00 VARIATION SELECTOR-1 is ignored after a transitively mirrored glyph

[dscorbett]

Font

NotoSansPhagsPa-Regular.otf

Where the font came from, and when

Site: https://github.com/notofonts/phags-pa/releases/tag/NotoSansPhagsPa-v2.004
Date: 2023-12-01

Font version

Version 2.004

Issue

A mirrorable letter (e.g. U+A860) which is transitively mirrored by a retroflex letter (e.g. U+A86A) but is separated from it by at least one other mirrorable letter (e.g. U+A868) is not affected by U+FE00 VARIATION SELECTOR-1. However, U+FE00 should always have a visible effect on the ’Phags-pa letters for which it is valid.

Character data

ꡪꡨꡠ︀
U+A86A PHAGS-PA LETTER TTHA
U+A868 PHAGS-PA SUBJOINED LETTER YA
U+A860 PHAGS-PA LETTER E
U+FE00 VARIATION SELECTOR-1

ꡪꡨꡠ
U+A86A PHAGS-PA LETTER TTHA
U+A868 PHAGS-PA SUBJOINED LETTER YA
U+A860 PHAGS-PA LETTER E

Screenshots

Correct rendering (BabelStone Phags-pa Book):