避讳

Imperial 避讳 was a serious legal matter — writing the reigning emperor's personal name was a capital offense. Scribes substituted homophones, omitted strokes, or rewrote whole passages. This is why the Tang character 民 was avoided during 太宗李世民 (Taizong / Li Shimin)'s reign.

mistakes

Two readings: bìhuì (full literary sense — name taboo) and bìhui (neutral tone, colloquial — 'avoid mentioning, refrain from'). Both are correct depending on context.