I can’t say anything useful about short-form email (I have never been comfortable with it, to be honest), but in IM the termination requirement feels to be alre

I can’t say anything useful about short-form email (I have never been comfortable with it, to be honest), but in IM the termination requirement feels to be already satisfied by the built-in separation between messages—in longer messages, I frequently end up using periods as statement separators rather than terminators. The only reason to use a final period, then, becomes to attach a feeling of additional abruptness or finality to the last sentence, which easily reads as (passive-)aggressive or dismissive. (I’m not saying “offensive” as that’s really more about the perception of the recipient, but these two are about the intent of the originator.)