isBrahmicFormatControl function
Formatting characters tolerated explicitly by the Brahmic parser: ZWJ, ZWNJ (zero phonetic output, never create/delete an inherent schwa) and CGJ (ordering semantics only, no readable output).
Implementation
bool isBrahmicFormatControl(int rune) =>
rune == 0x200C || rune == 0x200D || rune == 0x034F;