uh… medical lung scans show otherwise, but I’m fine with people destroying their own.

Exceptions to the rule don't make the rule obsolete. How many smokers do you know that could reliably run any distance further than 800m? I don't know any, but I do know plenty of people that quit smoking because it was inhibiting their exercise. Being a human that grew up in an area that normalized tobacco consumption and played sports, I've tried cigarettes. It absolutely affects performance in a very negative way. He completed the marathon in spite of his smoking, and would have performed better even if he stopped for a couple weeks beforehand and immediately resumed smoking after.

Don't feed the troll, guys. Either this guy is just playing with you, or he probably also believes the earth is flat or something. There are few things so well scientifically explored as the plethora of different negative consequences of smoking, so if he would be interested in realistic insights, he would stumble across studies and answers everywhere himself easily, so that is definitely not the case. Also, there are plenty of longterm extremely harmful drugs that might even increase ones performance short term, so this runner obviously didn't prove anything to anyone.