Nanoha. So, is her dad some kind of badass or something? Dude was chilling out and you could see scars all over the dude. So the only conclusion I can make is that he used to be some kind of badass.
Remember earlier in this topic (posts 448-450) when me and Itachi were talking about how the Lyrical Nanoha series was a spin-off of a completely different visual novel series? In that VN, Nanoha's father and older siblings worked as bodyguards, and the father was actually killed off at one point in the story. Him surviving is a change in the continuity from the Triangle Heart VN series to the main Lyrical Nanoha franchise, and the scars on his back are a reference to his shady past in the VN.
In other words, it's absolutely 100% meaningless as far as the Lyrlcal Nanoha franchise is concerned, only serving as a small shout-out to the original source material.
Ah, OK. Part of me was kind of hoping for some dramatic reveal that mister coffee shop owner is actually some badass Yakuza guy or hitman or something. I'll accept shady bodyguard though. That works.