This is an interesting Delenn vehicle, but JMS fails to capitalize on what the episode reveals.
The Lurker's Guide has a summary here.
Admittedly, this episode inspires in me a certain smugness. I mean, here we have the Minbari - a people favored by the Vorlons (and, at times, by JMS) - behaving like doctrinaire racists. "You can't marry Sheridan, Delenn! He's impure." And the Minbari are better than the Centauri how exactly?
Back in 2005, I actually proposed and participated in a sort of cage match at Dragon*Con that pitted the Minbari against the Centauri and asked the question, "Who is worse?" My position? Well, at least the Centauri tried to keep some Narns around to be their slaves and personal playthings. The Minbari, on the other hand, went completely ballistic and tried to kill everyone -- and I mean everyone. They even pursued the Humans who were trying to escape!
When we get down to the matter of personal guilt, though, that's when things get a little more complex. I think Londo is more culpable than Delenn because he made his fateful decision while calm and stone-cold sober. On the other hand, Londo ultimately apologizes to G'Kar and gets smacked by karma good and hard for his actions. Does Delenn apologize to Sheridan? We don't know because JMS never shows that to us. Now, I suppose you could consider Delenn's actions since the Earth-Minbari War to be tantamount to an apology, but JMS, an ex-Catholic, is quite clear on the point that the oral confession also matters.
But I digress. I definitely appreciate the glimpse at Delenn's backstory that this episode provides. I particularly enjoyed seeing how Dukhat shaped Delenn as a politician and philosopher. However, I think Atonement suffers because Sheridan is locked out of the proceedings. When Lennier discovers that Delenn cast the deciding vote which launched the Earth-Minbari War, there is no drama because Lennier almost worships Delenn and is therefore quick to excuse her actions. Imagine what would've happened if Sheridan had learned about Delenn's role in starting the war. Delenn has already gotten into trouble with Sheridan once for concealing Anna's fate. By all rights, she should've gotten into trouble again. Deceit does not a good relationship make.
As I note above, JMS should've found some way to bring Sheridan into the Dreaming. Other than that, the script is solid.
The performances are good, but certainly not flawless.
It's good that Delenn is working hard to make up for her past mistakes, but it's curious that JMS allows her to hide her guilt from Sheridan.
LENNIER: I wondered if you were going to leave without telling me. (He stands.) My place is at your side, Delenn.
DELENN: Not tonight.
DELENN: If you go, you will learn things about me that may change your opinion of me.
LENNIER: Delenn, I have pledged myself to your side come fire or storm or darkness or death. Can understanding be a greater danger?
DELENN: In this case, yes. (Ah, Lennier. Your love for Delenn is so cute -- and also so doomed.)
DELENN: If we do not know these humans, then they're a mystery to us. If the universe puts a mystery in front of us as a gift, politeness requires that we at least try to solve it.
DUKHAT: Ah! You're curious! You'd like to know, to simply understand. (To the others.) Simple curiosity! Ministers and counselors and warriors, and not one of you has the curiosity of the simple acolyte! Are you so jaded, so superior, so smug in your complacency that you've lost the simplest of joys -- that of the child and the closed box?
DELENN: Master -- may I ask a question? Will you make contact?
DUKHAT: No. The Council will be even more determined now. I could override their decision, but nothing would be served. Authority should never be used as a club, Delenn.
DELENN: Then why?
DUKHAT: When others do a foolish thing, you should tell them that it is a foolish thing. They may still continue to do it, but at least the truth is where it needs to be. They will be most upset with you now. You have embarassed them. I apologize for that. In my anger, I believe I may have caused you more problems in the future.
DELENN: No. No, Master. It was an honor.
DUKHAT: Don't interrupt when I'm being kind. It does not happen often, Delenn. (A beat.) Raise your eyes and look at me.
DELENN: (with eyes down) It is disrespectful.
DUKHAT: I cannot have an aide who will not look up. You will be forever walking into things. (And now Delenn's very first scene with Lennier in The Parliament of Dreams takes on a greater meaning. VERY nice!)
LENNIER: Then it was your order that began our war with the Humans.
DELENN: Yes. The Council was divided. Mine was the deciding vote. They killed Dukhat. I was furious. I never knew myself capable of such rage. All I could see was death.
LENNIER: Is this what you were afraid I would see? Then you are not thinking clearly, Delenn. The fault is not yours. The Humans misinterpreted the gesture of respect. They thought it to be the prelude to an attack. You were --
DELENN: -- the one who gave the order. Nothing can change that, Lennier. (At least she's morally centered enough to acknowledge that much.)