Three days after he was stripped of the gold from the 3,000m steeplechase final after removing his singlet in the home straight, the 27-year-old produced a stunning last lap to claim the 1,500-metre title, shooting past his rivals at the bell and entering the final 100-metre straight with a big enough lead to do a repeat strip.
This time, however, Mekhissi contented himself with gesturing to the crowd in premature celebration, before crossing the line in three minutes, 45.60 seconds — precisely half a second ahead of pre-race favourite Henrik Ingebrigtsen of Norway, with Britain's Chris O'Hare snatching bronze.
"My only possible reaction after the disqualification was to go back out and get this title," Mekhissi said.
"I guess today I wrote athletics history," he said.
"There are not many athletes who are capable of doing what I did.
"I came from joy to sadness after the disqualification and my reaction was the reaction of a champion.
"I had a lot of motivation. I ran with rage. I am very proud."
Had it not been for his rule-breaking antics on Thursday, Mekhissi would have been celebrating a double gold — just like Mo Farah was after the 5,000 metre final.
Having missed the Commonwealth Games in Glasgow after a health scare that left him hospitalised for four days, Farah returned to action to win the 10,000 metres on Wednesday, digging deep to fend off his rivals.
In the 5,000m, the 31-year-old Briton was more like the athlete who achieved distance doubles at the 2010 European Championships, 2012 Olympics and 2013 World Championships.
After starting at the back of the field, Farah made his decisive move at the bell.
He still had to work hard to resist the challenge of Hayle Ibrahimov but kicked away from the Azerbaijan athlete with 150 metres to go, crossing the line a clear winner in 14 minutes, 05.82sec, with Ibrahimov taking silver and Farah's British team-mate Andy Vernon adding a bronze to the silver medal he won in
the 10,000 metres.
"There have been some down times for me this year but getting two golds here is great," said Farah.
"There's been a lot of talk about me not being able to deliver but I've done my job."
Farah was not the only British athlete to deliver gold on the final day.
Indeed, there were five British victories in all, leaving the team top of the medal table with a record haul of 12 gold, five silver and six bronze — 23 medals in all.
France also won 23 medals but just nine of them gold.
The other British golds on the final day were secured by Olympic long jump champion Greg Rutherford, who prevailed with a fourth round leap of 8.29 metres, the men's four x 400-metre relay quartet and the men's and women's four x 100m relay squads.
The other relay, the women's four x 400m, was won with a grandstand finish by the flying French athlete Floria Guei.
Olympic bronze medallist Antti Ruuskanen of Finland won the men's javelin with a third round throw of 88.01 metres, while the veteran Spaniard Ruth Beita upset the odds in the women's high jump, setting a 2014 world lead of 2.01 metres to beat favourite Mariya Kuchina of Russia, who cleared 1.99 metres.
Italy's Daniele Meucci won the men's marathon in a personal best two hours, 11 minutes and 08 seconds but the loudest cheer of the day came when the Swiss team — including the retiring 2010 champion Viktor Rothlin, who finished fifth – stepped on to the podium to take bronze from the team race.