It turns out that when it comes to setting up shop in Destiny 2, the nomadic merchant Xur takes into special account the lighting conditions.
Bungie has confirmed that the vendor will never visit Mercury. The new location was introduced with Curse of Osiris and is naturally restricted to just the owners of the expansion pack. There was concern that when Xur does decide to head out to Mercury, the vanilla portion of the community would lose access for the specific duration. Thankfully, that will never happen.
Xur will continue to lurk around planets that every player has access to in the game. However, there is no guarantee that he will not be majorly selling wares from the expansion pack. Nonetheless, it is good to know that players will not be locked out from visiting him on a weekly basis.
Curse of Osiris arrived earlier this month and received a less than ideal reception. It attracted a mountain of criticism against the unorthodox locking of vanilla content that was already paid for when players bought the game back in September. This was due to the increased level cap, forcing players to purchase the expansion pack to regain access. Bungie finally addressed the matter this week.
The new change to Xur is just another step in that direction. Hopefully, the community will not have to see such dark days ever again.
Xur sells exotic weapons, armor, and shards. There are also the important engrams to obtain, as well as consumables and more. He appears in a different location every weekend when the weekly reset takes places for Destiny 2.