What are the restrictions on the use of abbreviations or procedural signals in the amateur service?
Only “Q” signals are permitted
They may be used if they do not obscure the meaning of a message✓Bonne réponse
They are not permitted
They are limited to those expressly listed in Part 97 of the FCC rules
Explication
What the rules prohibit is encoding intended to hide meaning, not shorthand as such. Q signals, prosigns and ordinary abbreviations are used constantly precisely because their meanings are published and understood.