@james I speak German, I partially use the screenreader on my iPhone (VoiceOver), but I'm sighted.
For _ (_innen, der_die, des_der, …) I set it up like this to read it as a short break: Einstellungen > Bedienungshilfen > VoiceOver > Sprachausgabe > Aussprache > + > Text: _, Ersetzung: ' (accent).
For * I could do the same but blind people can't safely because * marks mandatory fields. They could do *innen to 'innen, but this still misses out der*die, des*der etc.
Do not switch to : (too long)