[Buellen]

This is old one:

Merchant mining.

In the process of clearing out a visible slot you will sometime get another player come to sell stuff at merchant you are mining. You take the risk of that player buying stuff from slot you just clear if you close the merchant interface. Wait till the other player or players leave then close merchant window and reopen to see the new cleared slot item. The other player will not see as far i can tell the new cleared slot items so long as you keep your merchant interface open.

If you clear a merchant visible slot while someone else selling /buying form merchant and you close your interface with the merchant. You will not see the new item/items pop into the cleared slot till that other player/players leaves merchant interface and you reopen merhcant.