Is it permissible to write the Holy Quran with incorrect diacritics for the purpose of teaching people some reading errors?

You are not required to write verses with incorrect diacritics to warn people against recitation errors; this goal can be achieved without doing so. It might be acceptable for a teacher to write a word on the board and then incorrectly diacriticize its letters to illustrate the error, then erase it. However, there is no need for this, as errors can be corrected through other methods.