One thing I've noticed is that people who expect short replies sometimes write very short mails to begin with. I think that might be more effective to set expectations than coming up with a new acronym and having to wait for it to catch on (if ever).
If the content you need a short reply to is a bit longer, you can also write a short summary before the longer part. Something like "Below is blah blah blah, wondering if you have any quick comments. Thanks, yournamehere." Then below is your multi-paragraphed whatever.
I believe that Steve Jobs was one that practiced this when dealing with customers. And it seamed like his responses were always dead on target - whereas a PR team would launch into a long winded response to a customer, Steve summed it up in one sentence.
I've seen people who are great at short emails... but I've also seen a lot of miscommunication when people shoot fragments back and forth. It's a fine line between concise and useless.
If the content you need a short reply to is a bit longer, you can also write a short summary before the longer part. Something like "Below is blah blah blah, wondering if you have any quick comments. Thanks, yournamehere." Then below is your multi-paragraphed whatever.