Esta informação pode ajudar, não tenho certeza de qual é o seu conjunto de habilidades ou quais bloqueios você pode encontrar para tentar editar o arquivo.
The user-specific dictionaries for a language, which hold the content for the Added, Excluded, and AutoCorrect word lists, are located under %AppData%\Microsoft\Spelling\. The filenames are default.dic (Added), default.exc (Excluded) and default.acl (AutoCorrect). The files are UTF-16 LE plaintext that must start with the appropriate Byte Order Mark (BOM). Each line contains a word (in the Added and Excluded word lists), or an autocorrect pair with the words separated by a vertical bar ("|") (in the AutoCorrect word list). Other .dic, .exc, and .acl files present in the directory will be detected by the spell checking service and added to the user word lists. These files are considered to be read-only and are not modified by the spell checking API.