I've only once done a re: ad on CL. It was for a local bike seller who either lied constantly or had absolutely no clue. For example:

Batavus was made in Germany (maybe for a brief occupation period in WW2)
Tange Infinity is the equivalent of SLX or 531 (no it's not, it's seamed tubing)

and that's just a small sample. Every ad he posted was full of ridiculous innacuracies, almost all of them making the bike look better (Yes, he identified UOs as PXs at least twice). He'd put ads in fishing for a price, and various other dubious matters. Finally I made a post asking him to shut the heck up and just advertise his bikes, listing numerous innacuracies and distortions he had made over the prior month. He shut up, praise whatever.

I emailed a seller a while back. He was listing a bike, and I had seen it when he bought it. It had a major dent at the join of the headtube and down tube, not really a good place. He didn't show it, and called the damage a "cosmetic dimple". I called him on it, and told him he should put it in his listing, or just part the bike. But I saw no need to do a "re" on him, I just think he really didn't know.

It's good to remember that many CL sellers are not necessarily informed about bikes. Both of these example were regular CL sellers, although the first no longer really does-- his business practices caught up with him.