A few minutes ago I disconnected my computer from my network to try and reproduce a problem for someone. After doing so I plugged my ethernet cable back in, but stopped short of having it all the way in, and without realizing it was still not connected to the internet. I then went and replied via comment about my observations while offline. I didn't get an error when doing so and the enter comment textbox closed. A few minutes later I discovered that I was not in fact actually online, and that the comment I'd tried to post on superuser had vanished into the aether because there wasn't a page refresh involved for my browser to go back to.
I'm using Win7-64, and Opera 10.62.