There is nothing wrong with the truth. Once a lie is emailed, texted, or posted, as with all things on the internet, it remains a lie forever. It can damage your reputation along with the subject of the lie, and in a worse-case scenario, can be the cause of a defamation lawsuit.
Is your post motivated by deceit or truth? Are you concealing information that would be important to know in order to make yourself, the situation, or product look or seem better than it actually is?
Even when disagreeing with someone, it is important to discuss the issue or behavior instead of attacking a person's worth or dignity either online or in person. Additionally, consider all sides of the argument instead of just one to ensure you are giving the other person the benefit of the doubt.
The images and words you post of yourself and others should be those which are rated "G" for General Audiences which most likely will include college admissions officers and future employers. Their schools and organizations invest heavily in building their own positive brand images, and highly desire those individuals who will contribute to that effort.
When you think of others before yourself in what you send or post, you show that you value the worth and dignity of others. Always wait 24 hours before sending or posting anything written in anger. Sleep can do wonders for your perspective.
Did your message or post meet all of the above criteria? Additionally, when you defend those who have been marginalized or even take a stand for situations which might be counter-cultural, you demonstrate courage and strength of character.
Did you use the recipient's correct title: Mr./Mrs./Ms./Dr.? Does your language reflect your knowledge of appropriate modes of communication: informal language for friends and family; formal and polite language for teachers, employers, etc.?
A perfectly edited and well-written email or social media post shows that you value excellence, even in the smallest of details. Ensure proper grammar use through completing online practice exercises, using your word processing program's grammar/spelling checker, or even enlisting the aid of a friend to help you edit.