A problem has been spotted with the rendering of Tamil Brahmi vowels - in particular the sequence <U+11013 BRAHMI LETTER KA, U+11044 BRAHMI VOWEL SIGN O, U+11046 BRAHMI VIRAMA> does not conform to the grammar of the Universal Shaping Engine (USE); a dotted circle may be inserted between the vowel and the pulli.
When considering font-level remedies, I realised that there may be a problem with a following consonant - is <U+11013, U+11044, U+11046, U+11022 BRAHMI LETTER TA> a correct encoding of what may be transliterated as _kŏta_? The nearest to a convincing justification I can find for it to require U+200C ZWNJ after the virama is the text in TUS Section 12.1 for *Explicit Virama*, but that merely says that ZWNJ is required to produce explicit virama rather than a _conjunct_. As I understand it, a subscript final consonant would be encoded as consonant+virama rather than virama+consonant, so there is no ambiguity in Brahmi text. (If we try to make a rule out of two conflicting mechanisms, the difference might be that one is used for viramas and the other is used for invisible stackers, though that would require changing U+10A3F KHAROSHTHI VIRAMA back to being a virama.) The problem is that a font that tries to recover the situation might interpret <U+11013, U+11044, U+25CC DOTTED CIRCLE, U+11046, U+11022> as having TA subscripted to the dotted circle. If ZWNJ is required for _kŏta_, what text if any in TUS requires it? Richard.
