FWIW I am skeptical of this. I’ve only done a 5-minute lit review, but the psych research appears to take the position that subvocalization is important for reading comprehension. From Rayner et al. (2016)
Suppressing the inner voice. Another claim that underlies speed-reading courses is that, through training, speed readers can increase reading efficiency by inhibiting subvocalization. This is the speech that we often hear in our heads when we read. This inner speech is an abbreviated form of speech that is not heard by others and that may not involve overt movements of the mouth but that is, nevertheless, experienced by the reader. Speed-reading proponents claim that this inner voice is a habit that carries over from fact that we learn to read out loud before we start reading silently and that inner speech is a drag on reading speed. Many of the speed-reading books we surveyed recommended the elimination of inner speech as a means for speeding comprehension (e.g., Cole, 2009; Konstant, 2010; Sutz, 2009). Speed-reading proponents are generally not very specific about what they mean when they suggest eliminating inner speech (according to one advocate, “at some point you have to dispense with sound if you want to be a speed reader”; Sutz, 2009, p. 11), but the idea seems to be that we should be able to read via a purely visual mode and that speech processes will slow us down.
However, research on normal reading challenges this claim that the use of inner speech in silent reading is a bad habit. As we discussed earlier, there is evidence that inner speech plays an important role in word identification and comprehension during silent reading (see Leinenger, 2014). Attempts to eliminate inner speech have been shown to result in impairments in comprehension when texts are reasonably difficult and require readers to make inferences (Daneman & Newson, 1992; Hardyck & Petrinovich, 1970; Slowiaczek & Clifton, 1980). Even people reading sentences via RSVP at 720 wpm appear to generate sound-based representations of the words (Petrick, 1981).
FWIW I am skeptical of this. I’ve only done a 5-minute lit review, but the psych research appears to take the position that subvocalization is important for reading comprehension. From Rayner et al. (2016)