I wasn't crazy about the Lennier betrayal but it did track. Still, it was unfortunate and a little abrupt. In S4 Lennier was Sheridan's second in command on the White Star and they certainly seemed buddy-buddy enough, joking with each other and everything. And then when Lennier watches Sheridan and Delenn get to third base he teases Sheridan about it rather than being quietly seething with impotent rage.