Declan Cameron, 19, was convicted and sentenced to two 18-month good behaviour bonds for his role in late-night hits on trains at Otford and Austinmer stations, on May 31 and June 14 respectively.

However, this week he was let off on appeal after his lawyer argued a co-accused had received a bond with no conviction and, in the interests of parity, so should he.

Sutherland District Court presiding judge Paul Conlon told the court he believed the magistrate had erred in handing down such a lenient sentence, but reluctantly agreed to do the same.

The decision came three days after the conclusion of Keep Australia Beautiful's Graffiti Free Week, which highlights the $2.7 billion annual cost associated with criminal damage and encourages businesses and residents to report and clean up graffiti.

KAB chief executive officer Peter McLean said the court's decision was at odds with community attitudes towards graffiti vandals.

"There's a major problem with [courts] being either unwilling or unable to reflect community sentiment in this area," he said.

"The message this sends is that if you're caught you'll be let off, and that's the wrong message."

The attacks left a side of two carriages spray-painted with graffiti gang tags.

The court heard Mr Cameron acted as "getaway" driver in the Otford hit.

But he was an active participant in the incident at Austinmer, even wearing a Go Pro camera to film the group's efforts.

Mr Cameron will be required to be of good behaviour for the next two years or risk having the convictions reinstated.