Re: Fingers spread or together?
I've often seen it related, falsely in my opinion, to extending Ki. That's the most common reason I've seen in the past. It does look funny to me.
When I talk extending Ki in this way I emphasize through tegatana so the hands are actually tilted back slightly. (as in ikkyo exercise)
Mostly really to me it should be whatever the mechanics and natural flow of energy makes happen depending on what the hand is doing.
For example, if you use your palm, the base of your palm to strike then you will find the natural position of the fingers is to spread.