If you wish report in this thread if you've seen Mad Merchant vendor in Dalaran. Mad Merchant is a rare kind of vendor, that spawns only for certain amount of time, then disappears for a long-long time. It's quite rare to find him.
Spawn point place:
The easiest way to check if there's Mad Merchant spawned is to go anywhere nearby that spawn point, and type in chat:
If it targets it, it's spawned./tar Mad
Just an example of a report:
Mad Merchant spawned on realm Silvermoon. Last seen at 13:45 Server Time.
If moderators don't like the idea, please remove the thread. If the idea is overall not the worst to make this kind of thread, please don't flood it with useless information.