Make it explicit - VSR
A vs VSR
E, acceptable vs expected. But this makes the whole thing unnecessarily complex and I would prefer VSRA - I am fine with getting a very short reply. If it is not possible a, long reply is also fine but try to keep it as short as possible.
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.