nah : 12.2015 : Study: Ending texts with periods is rude and evil (Culture & Sociology, Internet)

Though written, the speed of response and the fact that the conversation is always ongoing means that texts are closer in nature to face-to-face speech. This means certain cues normal in most forms of writing, like periods at the ends of sentences, seem sarcastic or rude in text messages.

Source: Study: Ending texts with periods is rude and evil