I feel like periods mark the end of a sentence. So I use them all the time, even in text messages.
I've had people get actually angry with me for doing it.
I've had people get actually angry with me for doing it.
My personal nitpick is people writing a stream of one-sentence messages without punctuation instead of a longer structured message - that definitely carries the connotation of unstructured thinking to me - but it doesn't have much to do with full stops per se.