Recently, I've had a number of conversations that have been the result of serious miscommunications that occurred via email. I wrote an email and someone misinterpreted it, which led to that person writing something I didn't agree with and sending it to a lot of people, which led to me writing to an even bigger group of people, which led to the other person retaliating, which led to me retaliating. The spiral was out of control. And the problem? We were two people who had never met.
Writing is a tricky, slithery kind of communication in that we can't "hear" it. Imagine a simple sentence. For example,
"I'm going to the store."
A mom might tell her kids after school to find out what they want for dinner. Or a girlfriend might passive-aggressively tell her boyfriend who never pays for food or takes her out to dinner. Or a roommate might say to another roommate, rolling his eyes and ending another lengthy diatribe on current U.S. politics.
Thinking about the audience and the context, hopefully, changes how you hear that sentence in your head. It sounds different in each situation. But without a full understanding of that situation, if you don't know the person writing it or the circumstances they are responding to, it can be hard to "hear" the tone of the sentence.
Because we can't "hear" the tone of the sentence in writing as clearly, we rely on other signals to understand how information is intended. That accessory information includes formatting like greetings and closings and grammar like commas and periods and apostrophes. But those accessories can only do so much.
Our bodies are able to provide a lot of information that words simply can't: tone of voice indicates whether you are inviting or controlling or being annoyed, facial expressions and posture reveal your emotional and attentive state, gestures create emphasis and visually represent concepts, even eye contact (whether or not you make it) and breath can suggest emotion.
If you don't know the person to whom you are writing or whose messages you are reading, it can be hard to fill in all that supplemental information from just the words on the page. We try to imbue the word choice with meaning, called connotation, and use the punctuation to indicate breath and changes in tone, but these tools are limited.
In the following circumstances, consider carefully whether a written message is the most effective means of communication:
you do not know the person you need to communicate with
the content of your message may trigger some emotional response
the content of your message is complicated
If any one of these is true, writing may not be the best means of communication. And if all three of them are true, then you shouldn't even have to ask.