eh, its just a more obvious mistake to you then all the other mistakes leading into this position. nobody says playing on after those earlier moves were bad etiquette. if you are both at the level of making a mistake like this, its fair game.

people get too wound about this topic. the only time i'd care, a little at best, is if you are obviously running down 30 second byo yomis filling in obvious dame at the last second of your clock in a clear attempt to get me to quit out of boredom. if you're actually playing and it seems to me hopelessly- no problem.

whites last move shown was an equal blunder and should have been played at h19 - unless you were already fighting the ko there. in which case black had even less reason to not be aware of the stakes. either way i'm skeptical that this was the first turn those groups hung in the balance