Do you mean that the person you bought the tickets from had obviously misunderstood the context that they were posting messages into?
I follow a few dozen people and don't observe ~any~ misunderstanding that it is very public. There's people that like to share, but they are obviously clear on what they are doing.
I don't think the person misunderstood. I think they did realize that what they were saying was public, but didn't care too much - they just wanted to get a message to a specific person, and Twitter made the easiest way to do so to say it publicly.
As a result, a lot of such messages ended up being public, and while each of them was innocent, all of them taken together were saying a lot about that person. And the latter may have been an implication that the person didn't realize.
I follow a few dozen people and don't observe ~any~ misunderstanding that it is very public. There's people that like to share, but they are obviously clear on what they are doing.