Improper grammar drives me nuts. My mother taught high school English. So did my grandmother before she when on to earn her PhD in Botany and taught at the college level. I was raised getting my grammar corrected from both of them.
Now I correct everyone's grammar, from my daughter to the guys on the radio, the preacher and my friends, whether they can hear me or not. I know it drives them crazy and I apologize, my corrections are almost like an involuntary response.
The "I" and "me" personal pronoun error is the most common one I hear. Just yesterday I heard the afternoon guy on the radio say "...email Sue and I your contest entry...." If you take Sue out of the equation then you'd be saying "email I your entry" and you'd know that wasn't correct. Why does the conjunction make it so hard for people?
I knew someone in college who spoke poorly and would not heed my corrections, and would say she could say it correctly if she wanted. She was working on a degree in elementary education. She never got a job teaching. Who would hire a teacher who couldn't speak correctly?
Spelling is another matter entirely, however.
15 hours ago