The rules page states that battles must be at least 6 lines. This rule has been around since the site started. And what Empire said is pretty much spot on as how can you give an explanation with just 2 lines? You can create them, but if I see it, it'll get closed down. If you think about it, the chances of me coming across it is pretty slim. But when you have people reporting in Complaints that there are unexplained votes or something, it'll get closed with no one getting the win. In other words, if you create one, you both shouldn't report anything on the battle.