I know this thread is old old old, but I have to say I found this due to searching, and I have EXACTLY the same issue as Voltaire. I mean, I bruise all the time easily, but those two spots on my left bicep are always there after drysuit diving. I cannot for the life of me figure out what from. I've looked at how I move, what impacts, how I don/remove gear... I just don't get it!
I do bruise easily, and after a dive weekend I can usually count a dozen or so small ones that have no known origin.
Even stranger was last weekend, before day 2 I'm in the restroom and happened to look down at my left hand. There's a pea sized lump on the back of my hand, forming a triangle between my thumb and first knuckle. It was squishy, and BLUE. A friend with some medical knowledge said I'd just burst a capilary, happens all the time, and if it was fresh it would disappear under pressure. Sure enough, when I came up from the dive it was gone, and just a slight haze of a bruise in its place.
Kinda cool. =-)