On the contrary, I think its the best move he could have made
. As they pointed out, now its so much harder to kill L because then immediately Light would be a prime suspect and his percentage chance of being Kira would rocket. Just knowing that he's L keeps light from killing him, otherwise they'll know that it was him who murdered L. Not only does it protect L, but now he's even closer to Kira and can keep a better watch. Kira can do all the investigating he wants now, but I can't see how he'll kill L.
And about the episode, I thought it was very well done. Much better than last ep. Ooh I can't wait to see whats coming up.