I logged in this morning (moments ago) after leaving my trader offline overnight. Upon logging in I got the expected list of items sold. Displayed next is the usual note about the number of traders (6) and buyers (1) operating. After that it got weird. "That item is no longer for sale in the bazaar." That message appeared, then it appeared again, and again. It happened about 2-3 times per server tick for a full minute before it stopped. This was on the Brekt server. After it concluded spamming me I checked and there were four traders operating (I had not attempted /baz, /buy, /trader up to this point), so I suspect it had something to do with the two traders that stopped operating around the moment I logged in. I can only imagine how spammy this would be on active servers.
I have seen this happen when exiting trader mode from time to time. In my case the timing between the "item no longer for sale" messages sometimes felt like the time interval between a player constantly hitting the "buy" button in the remote-buying /baz window, and giving up after a few seconds. It sometimes started only a few seconds after exiting trader mode as I was on my way to the central bankers area to manage inventory. Maybe some other player was really desparate to buy something from the trader using the remote-buy /baz window *just* after we exited trader mode or something, causing this spam message to appear on the former trader character. Either way this message is strange to receive, so is perhaps worth looking into.
