The mods, while strict to the user agreement do give you several chances. I've been an RC member for almost 5 years, and a business owner for almost three. It's a constant learning curve to determine what crosses the "commercial post" boundary. I've been warned several times, by at least 4 or 5 moderators.
The best thing to do is not get excited about a mod's PM, and just take their advice, and not screw it up again. Reef Central is a privately owned site, that's the bottom line.
Stuff I have been called on:
Posting pictures after I owned a business
Saying, "We've got some at the store"
Directing someone to their LFS to look at a tank.
Discussing certain products.
Stuff that seems benign wouldn't seem that way if every business owner did it.
Also, I've never heard of RC staff banning someone for a first offense, ie, no "You used your one chance, yer outta here".
If you need store-specific stuff, PM or email the person. To ask in the open forums will just get someone in trouble if they answer, and you'll think they are being rude if they do not answer in the forum.