As JT has said in his first option – ignore it
A letter or email carries no consequence for you
Only a Notice to Comply has any standing, and it has to outline the by laws you have breached.
We all have different tastes and views, but if you had an aproval , in any form, you did the right thing.
When, or if , they issue you with a NTC , just sit on it.
Its then up to the OC to take it to mediation and to NCAT.
Its also up to them to prove they are right .
The other positive part if the OC takes you to NCAT, they have to pay the filing fee and then prepare a case. Most committees don’t know how to prepare an NCAT case so have to hire some legal advice, which means they have to get owner approval (as its likely to be above the $3000 threshold, even for simple advice.
If you win, then you cant be slugged for the costs incurred by the OC. If you lose the costs are split amongst all owners.
Just tough it out.