I find that most people read into text the way their behavior manifests itself. A sarcastic person by nature will likely read text and hear in their head a sarcastic undertone or inflection. Consequently a sweet person by nature probably doesn't take offense quite as easily, because they tend to see the good in people. I am probably as guilty of this as anybody. Also, many people don't have as good a grasp on grammar as others or are just kind of lazy when it comes to punctuation so again, things are misunderstood.
A perfect example is a T-shirt I once saw. It read;
Let's eat Grandma
Let's eat, Grandma
Using commas can save lives