Perhaps it was impolite to call it that.
The Aberoth community seems to be getting sufficiently paranoid about public trading. Someone listening in could leave the room, take off his clothes, drink an invisibility potion and get back in time for the trade.
Here is such a culprit caught in the act. I'm not sure why, or if, they need to be unfriendly.
The easiest solution is just buying an extra vault on an alt. It's only 500 gold and takes one minute.
Something to remember when trading in vaults is that dropping gold just deposits the money into your bank, and picking up gold is the same as withdrawing it. It doesn't matter whether you're in someone else's vault or not. I didn't realise this when I sold a pink pelt for 1k, but thankfully the other trader corrected it later.
I also did my first building work in someone else's vault. The first part of a "second floor".
Finally, I found out that there is a warning to the vault's owner when a visitor picks up an item.