[header] How to tell if someone is angry online [title] Pay attention to punctuation use. [step] Exclamation points, for instance, can either convey excitement, annoyance, or anger. Notice what they said and the context in which they said it to make a determination. 
[substeps] For instance " are you freaking kidding me? ! ! ! ! ! " can convey anger while " girl, the first day of school is tomorrow! " could indicate excitement. Periods can also be a sign of anger.