Officially known issues from the korean rebuild notice board, translated them for you guys.

[8/17]
▣ Some item images are not displayed properly or missing in Item Exchange

Icons of sealed mounts and pets(companion update things) are not displayed properly on Transaction History and Exchange completion window. The purchases and sales tabs should work well.

[8/03]
▣ Mailing system
- The Inbox was fixed to work properly, no server restart or patches needed.

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▣ Item Enhancement
- After item enhancement, item information is not displayed correctly.
The display error does not affect the result of the enhancement, your items will be enhanced.

▣ Skill / Tactic window
- The key shortcuts are not displayed on the Skill Information(K) interface.
The defaults for these are: [], [1,2,3,4,5,6,7,8,9], [R, T] in order from left to right.
- If you save the skill invested in the skill information window as a shortcut and open the skill information window again
you might experience wrong displayed skills in the skill information window.
In this case, just remove the skill and re-register, then save.
- You can invest up to 45 points on the right side of the skill information window,
It will be available in future updates.
- [Fixed 8/02] After investing in skills in the skill information window, there is an unusual decrease in the [skill points left].
The skill information window's displayed skill points can be reset on the character that has the problem when you modify skills.

▣ Production (Crafting)
- If you cancel the crafting process of an item, there is a problem that the item will not be crafted.
Please be careful not to cancel the crafting process due to movement.
- Professional item crafting quests are bugged, it might show [Quest in progress] even after completion of the item crafting.

▣ Taming / Companion system
- There is an issue with the taming system, where the taming mini game UI overlaps other UI parts and can't be seen properly.

▣ Enemies and hunting
- If you use the locate button(quest tracker) or auto-move to your custom marker, there are some monsters that roam around in a large area which causes the auto-move system to arrive at a different location.

▣ Auto Move System Issues
- [Fixed 8/02] When you select the icon of World Map and use the auto-move function,
A certain frequency may cause skipping.
If you set Auto-Move on the map until you edit it, you
Please set an empty space as your destination.

▣ Receiving waiting article box
- There is an issue where the waiting article box is not available through the item box of the system menu.
Items waiting to be picked up by amendment Items to be paid out will be considered for receipt by post. (?, could not translate this line properly)

▣ Exchange (Auction House / Marketplace)
- [Fixed on 8/01] It is not possible to register and purchase items, there are issues on the server.
It will be fixed soon.
After the modification is completed, you will be able to use the auction house after receiving the patch according to the notice in the game.

Source: link , link

"You will no longer be able to trade items through 1: 1 private transactions and mail."
They removed player trading completely, you can only use auction house now.
Also you can not sell enchanted items on the auction house yet.(this will be changed later)

Source: link

No words on how they will let users interact with eachother. It may become a Black Desert Online syndrome solo game.

Although, please note that these test server changes are not final and they may change them. There is a negative feedback wave on many topics about rebuild on the korean boards.