I'm saying that a modified runescape client can change how things are rendered i.e runescape names, interface texts, etc. So yes, in rare cases, video proof isn't sufficient.
The runescape client could be modified to render a different username than the one you're trading.
^^ 100% possible, and there's no way to find an "editing" flaw in that... unless he forgot to modify something in the client
it's extemely easy to modify something like this to fake a gold trade...