How does the reader know the difference?
Each thing that we do, speak, or write, is a display of who we are. Errors in grammar, syntax, and spelling, when typing or writing, can be easily corrected, but only if the writer takes the time to proofread. Not proofreading one's public writing is akin to not taking a glance in a mirror before leaving the house. Neither omission is fatal, and perhaps not even offensive to others; yet both indicate a certain lack of pride.
Pride is a personal commitment. It is an attitude which separates excellence from mediocrity.