As discussed in the localization discord, we came to the conclusion that the string #22755 "User Is Online in a Private World" refers to private instances as "private worlds", which could lead to confusion.
While technically not incorrect, as this could be interpreted as "the world this person is in is currently private to you, the viewer specifically", this can definitely be interpreted (especially upon translation) that the world itself is set to private and not that it's private to the viewer due to instance privacy and user status.
I strongly believe replacing mentions of "private worlds" that are referring to instances the user cannot access should be replaced with "private instance" to prevent translations of these strings being interpreted incorrectly. (Alongside it just being slightly more correct terminology.)
Here are all the strings I could find that refer to private instances as "private worlds":
  • #15139 "{0} is in a private world. Would you like to request an invitation?"
  • #22755 "User Is Online in a Private World"
  • #24093 "Online in Private Worlds"
  • #24101 "Users in Private Worlds"
  • #35264 "Online in Private Worlds ({0})"
  • #25569 "World is private"
    (This one might actually be due to a world itself being private but I'm including it anyway just in case, ignore if so.)
  • #25559 "User is in a private world."
    (I'm unsure about this one as well.)