Can you explain the significance of the Bhagavad Gita verse and the concept of 'Avagraha' as discussed in Chapter 50?

Chapter 50 references a verse from the fourth chapter of the Bhagavad Gita: "Tadviddhi pranipatena pariprasnena sevaya | upadeksyanti te jnanam jnaninastattvadarsinah ||". The text points out a subtle linguistic interpretation where an 'Avagraha' (a symbol in Devanagari script) appearing before the word 'Jnana' (knowledge) in the third line is seen as an indicator of 'Ajnana' (ignorance). This interpretation frames the verse as a discourse on ignorance. Without this Avagraha, the word is simply 'Jnana,' which all accept as the means to liberation. This discussion serves as a gateway into the chapter's deeper exploration of the nature of knowledge versus ignorance.