For people who say they will never leave a negative feedback:
Imagine, you got a PM from someone who wants to buy an item and is coming in 30 minutes. You are waiting even longer in spite of the fact you have something important to do. The person never shows up and doesn't communicate. Then, the same situation happens to you again with another reefer. You still don't leave any negative feedback? Chances are these people will do the same to other reefers. Aren't we here to help each other?
I'm willing to bet 9x out of 10, that same person will retaliate and give you a negative rating. It sucks but that's reality. Moving forward, people will see your negative feedback and might think you're a goon.
In general, I don't have time to be worried about small stuff like this. It's a hobby. Stuff happens. A long time ago, I sold a purple tang to someone. He came by early in the morning, and the day of, right before he got there, (of course) the poor tang got ich spots on him. Zero signs of it prior to that. I told the guy that I'd give him the fish for free and apologized profusely. he could have easily given me a negative rating. Instead, he was a stand-up guy, took the fish, and promised to pay me back if the fish lived. Reluctantly, I accepted. He saved the fish, (because he's the man and knows what he's doing) and ended up paying me back later. So it worked out for everyone.
The vast majority of experiences here have been positive, though.
If you're someone who gets all worked up, then I suggest only buying new equipment and fish/corals from a store, and not selling here at all. If you NEED to sell things to stay in the hobby, you might want to rethink things. Sorry but it's the truth. The hobby is just not worth getting stressed out over.
Another quick note: ever since posting "lowballers will be listed publicly", I haven't been low-balled once. I also try dealing with people I know personally or who have a solid, chill-attitude when posting on here.