I would suggest a [if touching color [], bounce] and [if touching [sprite1], bounce] blocks, so sprites can bounce from a certain color or sprite without having to (if <<touching []?>and<((direction))= (90)>? then).There are some problems though..
What angle is the sprite's edge facing?
It could be hitting something, at -135 degrees, but would it bounce off at 90 or -90? or even 135?
Maybe it could detect the pixels around it…
But would it be too much for the player?
It can determine what edge it is hitting on the stage…
But can it detect the edge of the sprite?
So many questions, so many answers, so many things could go wrong!

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How can you bounce off a sprite if the sprite doesn't always have straight lines with definite curves? And you can't bounce off a color for the same reason. Only the edge works because it has a definite slope. You can always use your own workaround to get the effects you want, but it would be too confusing for newbies because they may want different things.