I manage a small (less than 200 members) e-list pertaining to one of my hobbies. Recently, a member (let's call him David) posted, saying something like, "Look! There's a cool thingmajig for cheap on eBay!" (the thingmajig being one of the primary things we use in our hobby). Another poster eventually pointed out that David was in fact the maker and the seller of the thingmajig, that it seemed odd to not simply mention that - and that this was at least the second time he'd done so. I looked in the archive, and his previous mentions of his sales really gave the impression that he was just someone who had noticed the item, not the maker and seller. Additionally, he's never posted on the list in any other way, and most of the list has no idea he's a manufacturer of said thingmajig.
It made me uncomfortable enough that I wrote him a brief note, saying it was important to avoid the appearance of stealth marketing and asking him to identify his interest in future announcements. I also wrote a more general note to the list as owner/moderator, giving some guidelines for announcing items for sale. Now there's been a considerable private email exchange, where David is pushing back very hard about the issue. He's not saying he refuses to follow the guidelines, but he's arguing the issue. He says that he doesn't say it's his thingmajig so his work stands on its own merit, that he refuses to participate in the ego of saying "I,"; I say that he's giving the appearance of stealth marketing and of obfuscating his true purpose in bringing the item to the list's attention. I'm not telling him that he's a bad person, but that transparency in marketing on the list is better. I'm trying to be polite to him but he's starting to get on my nerves, for instance, saying something like, "Thank God not everyone thinks like you!" which really struck me as offensive.
Now he's trotted out the old saw of "I've received so many emails" saying "What's her problem?" to try to undermine my position. So I wanted to ask the EHellions opinions - is it really perfectly okay to post about a sale like that, without admitting one's own connection to the item? Or is it at least a little odd, and potentially deceptive? Obviously, I have the right to run the list the way I see fit, but I do want to be fair.