The swimmer this week used Twitter and Instagram to express gratitude to one of his eagle-eyed admirers who had emailed the swim team doctor to say Horton should get the mole checked.

"Good call. Very good call," Horton wrote, underneath a photo of him wearing a bandage on his chest near his neck and giving a 'thumbs up.'

But some people have clearly not forgiven the 20-year-old for his previous outspoken stance about drugs in sport - at the Rio Olympics he outraged Chinese swimming fans when he called fellow gold medallist Sun Yang a drug cheat.

At the time he did not retract or apologise for his comments and team administrators supported his stance.

After Morton posted online about getting his mole removed, many people found an opportunity to attack again.

In some of the comments below his Instagram post, he was called an idiot and some others also said they hoped he would die.

"Hope u loser die soon," one poster commented.

"You Are A loser forever," another said.

Someone else posted this: "I got a bad mood after see your picture."

Another commentor offered this: "I'm so sick seeing his idiot looking picture."

It will seemingly be a while it seems before the Mack Horton-Sun Yang feud blows over.

Fairfax Media has approached Mack Horton's manager for a response.