Scott basically said after the game that he didn't like how the previous fight went down and it was his job to send a message about it. He said he was going to go whoever lined up with him and was surprised that Carlyle sent Kessel out. So, I'm pretty sure that Kessel didn't instigate anything.
Personally, I can see what Carlyle was doing by sending Bozak and Kessel out. Unlike the Devils-Rangers line brawl from a couple of years ago where each team loaded up their brawlers for the opening face-off, he was trying to prevent things from escalating. He figured that sending that line out would let the Sabres know he wasn't interested in having a slug-fest in the preseason.
It obviously didn't work. Made for good entertainment, anyway. I despise the Leafs (have so all my life) but can't believe Scott couldn't have picked a fairer opponent to 'send his message'. I know there's alot of discussion of whether he broke the 'code' for fighters, and based on the evidence available, I say yes. He will have to answer to Orr and McLaren, and likely both, next game.
Although Scott shouldn't have gone after Kessel, I still give Kessel 1 or 2 preseason games suspension (probably 2, just because 1 preseason game is essentially meaningless). I'd turn a blind eye on the first slash and maybe even the second. Coming back at the end and trying to spear Scott puts it over the edge along with the match penalty he got for it.