So it is possible to see a player at an unexplored wormhole.
(I haven’t been here yet.)
What seems to have happened here is that this user has travelled to the “star system” the wormhole is at but has not actually docked in orbit around the wormhole.
So they are still visible.
(In fact, zooming in closer there was another player I could see, but their location was hidden as it ought to be.)
@samuelronban seems to have beaten me to spotting this issue: his screenshot is actually of the same wormhole and I suspect that Ultimate DODO has been sitting there for some time.
I am only reporting this again because the previous one had very little context as to what was actually causing the bug.