Accommodations are merely tools. They should not change the nature or the underlying quality of response, but allow access to the optimal performance of that person. You still need a skilled person to employ the tools.
If an individual who may lack the skills to instruct children in spelling and punctuation manages to obtain qualifications to do so, with or without accommodations, that is a separate question. Also, if the particular person referenced previously used accommodations in spelling and punctuation to obtain her position, then she should continue to use them in maintaining her position--in which case these errors would not be transmitted to her students.
Actually, quite a lot of teachers of language arts at all levels have dyslexia--but they may still be excellent teachers in their field because of their strong language comprehension and expression skills outside of word-level mechanics. Flawless spelling is not a prerequisite for high-level literary analysis. But it helps to be able to acknowledge one's own vulnerabilities, and be willing both to use tools and to receive corrective feedback.
