A poignant look into Delenn's history and the one truth about herself she feared the most. But the fact that she's tormented by this (quite understandable, especially with some human in her) emotional outburst, just goes to show that she is of course a good person who can easily be sympathised with.
I'm curious whether Sheridan knows the full extent of her involvement in starting the war - I'm sure he'd understand, I just don't think secrets like that would be a good thing to go into marriage with. Perhaps that's dealt with later (or perhaps it has been - I took a break and forgot a few things).
It's a little odd to think how there were kind of hints of romance between her and Sinclair in season 1 - it was open to interpretation as a platonic love I guess (like how Lennier excellent explained his a handful of episodes back) but it's just a bit of a mind bender to think that if it'd have gone further she could've ended up with the child of her great great great great grandfather or something :p
Interesting also to get more insights into the Minbari. It doesn't paint the desire to be "pure blood" as nasty and bigoted and in some cases outright evil as the Harry Potter stories do, but the message is still there in a subtle form.
This episode's comic relief comes from G'Kar's really camp exclamation of "it's not my proper colour!!" - oh you lovable Narn, you.