My brother and his wife are sign language interpreters speaking American Sign Language (ASL). ASL is its own language with syntax and grammar and the signs are not merely replacements for English words. The deaf who use sign language and who also read are really bilingual.
So that got me thinking. How is someone who doesn’t hear able to read? Written English is largely phonetic with the letter symbols representing sounds. When you can’t hear sounds, how do you conceptually manage these very abstract symbols that have no meaning in a non-hearing world?
I found some answers here. It seems that the deaf process the words as a whole and not through their component parts, relating the whole word as a symbol for the related sign. As a result, they do not confuse homonyms (words that sound the same, but are spelled differently ex. your and you’re). But they do confuse words with similar signs (ex. tea and vote).
They would also need to develop a certain familiarity with English grammar, which is different than their own, so that they could make sense of word order.
It’s hard to wrap your mind around.