It seems like homeless people give the best comments, based on this thread.
I never had a comment from a homeless guy, but one stole my gloves while I was doing a track workout once. They were running gloves, not generic ones, and I saw the guy walking around during my workout; I kind of felt like he would do something. He took them off the picnic table I left them on, but he left behind his gloves that had three holes in the fingers. I was kind of mad at first because I had to run back to the school with no gloves, but now I'm glad he took them because his gloves were so old.
I get lots of comments while running in harsh conditions. I don't remember them all, just two really.
One time during a heavy snowfall (not a blizzard, just big pieces of snow falling at a good rate) I got a "That's dedication!" comment during my run.
Another time when I was a mile away from my house a freak storm caused it to absolutely POUR down. It hurt to keep my eyes open and I was running while looking at the ground. A passing car offered me a ride but by that point I was only a half mile away from my house so I declined. The storm ended by the time I got to my house and maybe the sun even came out? (I forget exactly) If it had started hailing I would have gladly taken the offer.
Running regularly by a high school when they get out yields some comments that don't really need mentioning, use your imagination.