I was editing an answer (my own, but I do not think that's relevant) while someone else saved his edit on the same answer.
Now, I got the notification bar for new changes that could be shown, above the form where I was writing in.
Being aware of the conflict, but somehow trusting the near-perfection of this software (that's not a joke) I clicked the bar to load the conflicting edit, at which point my form content, a refinement of the answer, was lost.
I would not call that a bug, technically it was not that surprising that the question really was reloaded. But I see a UI imperfection at least. And because it's about loosing data, I feel it's worth writing it down.
First: Is that possibly a local problem with a strange browser configuration or so? Assuming it's not:
Trying to reconstruct why I interacted that way,
one factor is that the refresh notification bar it something known, and normally non-destructive.
The effect is, in other places: "The page layout may change, but nothing dangerous will happen".
Most importantly, I can refresh an edit on a different answer while editing mine in a form on the same page.
Was is also the intuition that there would be either a warning before, or a confirmation request after triggering a destructive action.
Or, alternatively, some opportunity to resolve the conflict.
The situation with two persons editing at the same time may not be very common, but it was not just by chance:
I had requested someone to write something as a separate question. I already had the solution at hand. Now, I posted that as a short draft answer, and started to take my time to fill it with details. Now, someone pointed out an error in the short version, and just fixed it - which is perfectly right, but created the edit conflict as a side effect.
With this situation in mind, I'm at least not sure it's so uncommon that it is irrelevant.
Related, but not duplicate: Issue with a lost edit
There, the edit conflicts with itself on save. In my case, there was no save from my side involved.