I like this idea, but I wonder about the phrasing. I wouldn't want my more... loquacious colleagues to misinterpret it as an imperative ("please do not send me a wall of text").
Different suggestions from the comments.
CURT - condensed unfussy reply tolerable
CURT - CURT unfussy reply tolerable
NLRN - no long reply needed
TCRA - très courte réponse attendue
VSRA - very short reply acceptable
VSRO - very short reply okay
VSRW - very short reply welcome
That got forked quickly. And we need a standardization committee. Or maybe a poll will do. VSRW - Very short reply welcome CURT - CURT unfussy reply tolerable BRIF - Brief response is fine