Luton had striker Steve Howard and manager Mike Newell sent off as they slumped to a second successive defeat.
Howard received a straight red card on 56 minutes for foul and abusive language towards linesman Jarnail Singh.
Mike Newell received his marching orders from referee Phil Crossley in curious circumstances on 72 minutes.
The ball was running out of play by the dugout with Brighton's Nathan Jones pursuing it when Newell stepped in.
Her explained: "The ball had gone out. I was just trying to stop it so that I could get the ball back into play.
"The ref said I stepped outside the technical area. There was nowhere for me to sit, so I had to stand in the tunnel for the rest of the game." Newell will fine Howard for his verbal indiscretion when Luton were only 1-0 down.
He said: "I cannot accept that. We can not afford suspensions and ill discipline." Brighton, missing three key players through injury, went ahead in the 16th minute. Jones, playing against his old club, crossed to the unmarked Darius Henderson at the far post.
Henderson's low drive was missing the goal when it was deflected in by defender Chris Coyne.
The Seagulls then clinched victory five games from time as Charlie Oatway netted a second for Steve Coppell's side.