I think it'd be nice if the wishlist had some sort of functionality that allowed a user to see how many items from a different user's wishlist they already own without having to manually check each item.

Even something as simple as a different border around an item in a wishlist signifying you already own that item, I think, would really encourage gifting.

There used to be a feature similar to this on wishlist (WL). It would show text below the image saying something along the lines of "You already own this item." However, it caused a significant strain on the servers because when a person loaded a WL, the feature forced an account search for each and every item each and every time. It was causing the site to freeze and/or crash for several users when they viewed WLs so the staff removed it.

What you are suggesting would be pretty much the same situation (i.e. it would require the account search), just with a color change to the box as opposed to the addition of text.

I would love to see it come back, especially now that they've implemented a limit on how many items can be added to a given WL but I doubt it will happen. (Possibly because it would still cause similar - if not the same - problems. I imagine they would have to restrict WLs to a fairly low number for it not to be an issue.)

Ah, I never considered the potential strain on servers doing checks like that would have. That's unfortunate, but completely understandable.

I do miss the feature that Aeon mentioned tremendously and not having a replacement at all for so many years really sucks. Every time I take a long break from the game, I come back hoping that there will be something comparable to it. Perhaps they could use something similar to the shop queue to concoct a replacement:

You press a button on the other person's wishlist to search your account for items on that wishlist that you own (similar to the button in user shops that shows only items that you've added to your wishlist), and it will be queued -- based on current server strain and size of the wishlist it might be fairly fast or you might have to wait a few minutes. After it completes it would give you a link to a page containing only the items you own, broken down into multiple pages if necessary.