Misspellings could be as a result of typing errors (e.g. the transposition error teh for that), deficiency of familiarity with the normative spelling, or not enough issue around spelling rules at all. Whether or not a word is misspelled may rely on context and also the orthographic conventions adopted, as https://dslspellingmistake93714.thechapblog.com/26425941/a-review-of-spelling-mistakes-in-english