Such things happen here more frequently - their usuality depends on the area and it's inhabitants.
Turning away without correctly finishing the dialogue was almost always a sign of an incoming attack in my experience. When they turn away, I usually step one step diagonally back and grab one of my weapons, ready to draw it with another backstep would the possible attacker really attack. They usually turn far too much, thus they lose track of me for a moment, thus they usually become rather deconcentrated when their punch (or kick or whatever) fails. They usually have enough time to realize the blade in my hand, so most usually such conflicts end with the attacker going away. There were only 2 occasions so far when I had to actually use my blade, both were caused by either the attacker's intent of following me or their more proper distance judge. Both cases ended with a cut placed cca at their wrists-hands, after which both attackers retreated.
Luckily here most attackers are very unprepared and not motivated enough to endure such harsh responses. This combined with the amount of training we do results in a feeling when you wait for the nuke to blow up and it's only a petard. Not as if I'd have any problems with that...
...
About restaurants: I love those with mirrors inside. We always pick our table according to visual cover of the area, available makeshift cover and weaponry, escape routes and such. This may seem a little paranoid or strange, but after you get used to it, it's close to nothing. And having a few violent crimes (I mean those that happen at such a place that they deserve mention in the media) every year convinces most people who would label us idiots. Friends don't have to be convinced, some of them wear more hardware than me.