Hey, halitosis worked for Clark Gable.
Gable had false teeth. Vivien Leigh did not enjoy kissing him.
Gable was somewhat lax in his hygiene, even for those baths on Sunday times.
Yes, I saw It Happened One Night. He reminded me of a Russian with whom I once had to share a cabin. Phew! 
The way I read it several years ago was George C. Scott telling an actress “One of two things is going to happen. I apologize in either case.”
Funny as hell, whoever said it.
There’s a surprisingly large number of people who view kissing as more intimate than actually having sex. If you go on certain parts of Reddit, Youtube, etc., you’ll find prostitutes who say that they refuse to kiss any of their customers. (And no, it’s not usually related to fear of disease; it’s a perceived intimacy issue.)
Yeah, that’s an old trope or whatever you want to call it. It was even in Pretty Woman, if I remember right. (Well, it’s not really so much a trope, as it’s not just a literary/narrative/dramatic idea, but the whole “prostitute that won’t kiss” is common enough an idea in mainstream culture, I think. At least I’ve pretty much always been aware of it.)
If I understand correctly, open mouth kissing in acting does not involve the use of the tongue (unless, I suppose, it’s being done explicitly for the camera). That’s one way that there is a distinction in “intimacy” between an acting kiss and the real thing.
I work in the theatre and have a small amount of training in intimacy choreography, and have worked with experts in that discipline. The field of intimacy choreography has come a long way in the last 10 years, and it is now fairly standard in film and on stage to have a choreographer ensure those scenes are done safely for everyone involved. The main techniques are, briefly, rigorous consent for every action, keeping every little action very specific, and keeping the language de-sexualized, e.g. “I am going to place my right hand on his hip, light touch, pull toward me a quarter turn,” etc. The actual language is generally a little more technical than that, but just to give an idea. These scenes are highly choreographed, like dance, and keeping it very technical removes a lot of the loadedness. The trick for the actors then is to then make it look like it’s super sexy (assuming that’s what you’re going for in the scene).
I read that it was Wallace Beery whose personal hygiene caused his actress costars to dread their romantic scenes. Maybe there were several leading men who needed a best friend to tell them…. Or maybe it was a Hollywood way to disparage an actor.
Lip-readers to the fore: While Aileen Pringle was being lovingly carried by Conrad Nagle in the silent film Three Weeks, and was supposed to be whispering endearments, she was telling him “If you drop me you bastard, I’ll break your neck.”