DC notes that they do not engage in silent or other subvocalization while reading, with the result that much of DC's vocabulary acquired purely from text does not even have a pronunciation (in their mind) until DC decides to use it in conversation.
My early childhood was spent in another country where the remnants of the British empire left a legacy set of rules for pronunciation which differed from the rules of the local dialects. Immigration introduced me to a fourth set of rules, so it might be that I subconsciously shied away from subvocalisation to avoid these conflicts. I am mindful to vocally practise delivery of my lectures & presentations, otherwise I can actually surprise myself when the words are vocalised and then I�ll repeat the word(s) with different pronunciation and entirely lose the flow of my presentations.