I haven't, but recently on two occasions I've really wanted to.
Last week the small train carriage i was in stank of wet dog really strongly - two women in seats opposite. I thought they just need to clean the carpet. Cue 2 days later, one of the same women again and bad smell again.
Yesterday in a store I got a strong wiff and there was someone beside me. Went to another part of the store and the smell returned when she did.
Obviously I said nothing but if it was me I think I would want to know. The lady on the train was with a colleague or friend- it must be very difficult for them - the smell was overpowering. She was talking about having ten puppies - they must be peeing on her coat!
Would you ever say anything? I'm probably going to smell the train lady again.