You are giving this guy some REALLY unsound advice. Totally incorrect information.
It definitely ruffles my feathers, on several levels. One is that what you are saying could cost this guy a jet, if he followed your advice.
The other is it is a slap in the face to hear somebody sound like you do, all high and mighty, just because they have not yet had the pleasure of being beaten up yet on the internet for no good reason at all. You are telling people:

"I would be weary with only one bad feedback.
I make sure not to get any bad feedback by being as totally honest with my customers. "
Well, that's just not reality. It's totally out of touch with reality.

I think it's a fair assumption to say that I have sold more than you...you would not say what you are saying if you have been around on the internet long enough. I have had the dubious pleasure of seeing pretty much ever form of scam and every type of knucklehead out there, and I talk regularly with the ebay powersellers, and we share a lot of info. There are some pretty harrowing people out there.
How about the guy who just negged me last month: This guy's scam is to complain that there are missing parts and ask for a substantial partial refund. I looked at the feedback given by him and gotten by him, and realized he was pulling a scam. I looked in my photo file and found that I had a picture CLEARLY showing the LG he claimed missing right there in the box. He was LYING. He wanted to get $25 back on a $100 kit. I called him out on it, and he refused. He negged me. Am I now a dishonest guy? Are you now wary of buying from me? Should I have just sent the guy $25, and let him keep doing it to other people(he did the same thing to several other people I know)? Did my own personal integrity protect me from getting a neg? NO. So please don't make facile statements like "if you are honest you won't get negged" because it just ain't so. And if you transact on the web long enough you will find this out the hard way.