The Batak script has a peculiarity which sets it apart from all other Indonesian scripts. In closed syllables (CVC) where the vowel is not an /a/ and has this to be written using a diacritic, then this diacritic is NOT placed after the first consonant, but after the second consonant and before the pangolat (virama).
Let’s look at the word “inon” which consists of two syllables i+non. The second syllable is non, which is a closed syllable in which the /o/ has to be represented by the diacritic [o] which has the shape of an x. The word consists of the following five graphemes: 1. Akshara [i], 2. akshara [na], 3. akshara [na], 4 diacritic [o], 5 virama.
Initially when the Noto font was designed, it had a smart algorithm built in which automatically re-rendered a typed sequence na+o+na+virama to na+na+o+virama. This worked quite well, but only when the Noto font was installed. Nowadays, however, the majority of users use the Internet where the smart algorithm did not work.
For some reason this smart algorithm was then dropped.
Now, when we use the Noto font in a word processor, and we type inon with the last syllable as na+o+na+virama, the output is rendered as in the following image. This is wrong.
When we attempt to write the second syllable of inon the correct way, namely na+na+o+virama then this is marked as wrong.
The same happens when we use the Batak script online. The input ᯤᯉᯬᯉ᯲ is WRONG but Noto allows it.
When we type ᯤᯉᯉᯬ᯲ Noto regards it as “wrong” by adding the small dotted circle.