I am Australian. Remember those Energizer bunny commercials showing the other bunny running out of battery halfway through the race? And a quick google shows that Duracell ran a direct campaign against Eveready which was ruled ok by the courts, as well as a recent court decision in favour of Optus doing direct comparisons with Telstra for mobile phone plans.

To be clear, I do not believe the parent post who said 'this is not allowed in most countries'. I would be less surprised by a claim that this kind of advertising is uncommon in most countries.