I suspect that because most text messages are to people that we know well, then we don't think about our audience so rigorously when we are texting them, but this is misleading. We are forgetting that we already have a long history of interactions with this particular person. We have already done lots of thinking about them, so we can reliably intuit on-the-fly the kinds of information they need and the level and style of language that they will accept from us. For instance, if I'm texting my wife, then I can casually refer to Maddie, knowing that she will immediately understand that I'm talking about our granddaughter. I could rely on my colleagues or students having the same understanding. Maddie simply doesn't mean the same to them as it does to my wife and me.
When we fail to frame our text messages for a given audience, then we run the risk of serious, sometimes damaging, miscommunication. We all know an example of someone, maybe even ourselves, who has sent a text message to the wrong reader with disastrous consequences. Google "misdirected text messages" to find tons of similar text messages:
So what's the lesson here? Always know your reader. I college, you are often writing to a teacher, unless otherwise assigned. You should know what the teacher is looking for in their communication with you. If you don't know, then you should find out BEFORE you submit your document for grading.