It does matter Antony.
And all clearance are written in short hand so not much room there.
A typical written clearance from MAN would P1Y 4563.
Spelling does matter. Most information is passed on by written form so its documented. If you write it down like a chump. Everyone presumes your a chump.
Bloody hell one of the worst offenders for crap spelling and grammar is lecturing someone why you should make the effort.
MJ