SOME LINGUISTS LOOK AT PERIODS IN TEXTING. I posted here about how “um” and “uh” are used in conversation as a signal to show that the speaker is not done.
Lauren Collister on the Quartz website writes here about what seems to be a similar convention which has developed for texting. She argues that a period at the end of a text message can be rude because it suggests that the conversation is being ended unilaterally, perhaps abruptly. There is also some evidence from researchers that the use of a period at the end of sentences is often taken as a sign of insincerity, apparently because it seems excessively formal. It appears that with texting the use of periods is following the conventions of speech, rather than of writing.
For myself, I have trouble with small keyboards. When I am texting, I always try to put a period at the end of each sentence. Sometimes I succeed and sometimes I don’t.
The other signal I use is a capital P, which often signals that I tried to hit “send” and hit the wrong key.