This includes cooking odors, insence, sweat sox, meth labs, dead bodies and smoke.
There is no place, that I know of, on the Appraisal sheet, for a remark about smoking; although there should be.
I have had buyers enter a house, take one whiff and turn around and leave.
Good luck on telling them to stop. Yes, certainly try. Don't expect any success. It's not an issue of dollars and cents (or sense!). They're addicted. If they're only light or moderate smokers, you can suggest that they only smoke outside. That sometimes works.
Ozone machines can remove much of the smoke smell from a house. (Hotels use them when a smoker occupies a non-smoking room.) You can rent or buy the machines. It's more cost-effective to buy. For an open house, you'd run one or more machines for 3-4 hours, ending an hour or so before the open house. Note: Ozone can kill plants and animals, so the house has to be empty when you're doing an ozone blast. But it breaks down quickly, while the odor-killing effects remain.
Hope that helps.