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.)

The conventions for formal messaging and informal messaging are different, and punctuation is a contextual marker for formality. Receiving a reply to a physical letter that read, on company letterhead and with a physical signature

    Taxcoder, regarding your proposed changes,
    
    Ok.
    
    Sincerely, Jim Bossman

would be a bit alarming, because it's clear that the letter is a very formal one, but it deliberately omits everything you'd normally put in a letter. If you instead found your proposal mailed back to you with

    OK - Jim Bossman

written on the bottom in red pen, you wouldn't be at all worried, although depending on the context you might be insulted by the informality.

I think if a message without punctuation seems sloppy, the situation is formal enough to write a full sentence or paragraph. The combination of little to no feedback and attention to detail is what worries people.

"Ok" is ever more informal than "Ok." The decision whether or not to add the period is of course not always a matter of trying to sound more assertive, but in a three character message that potential cue will necessarily be "scaled up".

It depends on the message. A longer form message with punctuation is fine. In short messages, the period is read as an aggressive sudden stop.

My last manager would frequently message me "Ack!" after I would bring up some work concern, and until just now I thought he was making the exasperated sound from the Cathy comic strip.

by abbreviating, it seems like you value your own time higher than the other person, like their message is not worth writing a whole word in response. At least, that's how I might feel about it. That and it feels a bit like that sketch in The Office where Kevin drops all his interstitial words for "efficiency" and ends up sounding brain damaged.

Obviously that's not the intent, but as per the article, work-related IMs and emails can heighten negative perception and such.

not offensive but it can be read as dismissive. sounds good to me or will do seem better, but tbh chat generally sucks and we all just have to learn to not read too much into it.

Maybe you just haven’t realized it’s being used that way?

Examples:

“It’s fine!” (It is indeed fine.)

“It’s fine.” (It’s not at all fine.)

“K, thanks” (Got it, thanks)

“K. Thanks.” (Cool. Thanks for nothing.)

“Bye” (See you later)

“Bye.” (Fuck off)

Think. About. It.