One thing I know for certiain - smoking is unhealthy. But there are also a lot of things that are unhealthy. An unhealthy diet could lead to high cholesterol to heart disease. Having a buddy that fits into such a category would be scary - I'd hate to have a buddy need to be defibbed while 50' under
However, an unhealthy diet is not as obvious as someone who smokes, you don't have to know their health history to know if they are a smoker. One of my frequent buddies is a smoker and a lot of my friends smoke. It's their choice. I also know that this buddy is a competent diver and I trust him and have no problem with him smoking, although I encourage him to quit.
Vlade Divac and Pele smoked and are (were) good/great athletes. Smoking doesn't necessarily make you a diving hazard. I guess it comes down to how well you know the person and whether you trust them or not - which seems to be the route you would take regardless of if they were a smoker or not in chosing a buddy.

Vlade Divac and Pele smoked and are (were) good/great athletes. Smoking doesn't necessarily make you a diving hazard. I guess it comes down to how well you know the person and whether you trust them or not - which seems to be the route you would take regardless of if they were a smoker or not in chosing a buddy.