I've been thinking over this topic since it first appeared, and for the life of me I can't come up with a definition of "hero" that makes sense.
It must be one of those ancient words that has morphed meaning over time.
"Show me a hero and I'll show you a bum."

One thing I can't buy into is that JWB was a coward. What is the brave way to kill a president? A duel? With a spoon as he wields a broadsword?
I suspect that any man who would shoot a president in the midst of hundreds of his supporters, then leap to a stage below to address those supporters, would have absolutely no difficulty challenging you to a duel if you insulted him or back down from a challenge.

Should JWB have asked Lincoln to turn around? I imagine if it were possible to shoot Lincoln in the face JWB would have much preferred that I think.

So I have to say no, he was definitely not a coward.
As for a hero, I can't even define what the word means.
Can you?

Did Lincoln deserve to be shot? Only by every Confederate he came within range of.