[chasil]

The primary thing to know is that the actor who played Sinclair in season one, Michael O'Hare, suffered from mental illness.

https://en.wikipedia.org/wiki/Michael_O%27Hare

His treatments were only partially successful. He reappeared in a cameo appearance early in season two ("The Coming of Shadows") and returned in season three for a two-part episode ("War Without End") which closed his character's story arc. At that time, Straczynski promised O'Hare to keep his condition secret "to my grave". O'Hare told him to instead "keep the secret to my grave", arguing that fans deserved to eventually learn the real reason for his departure, and that his experience could raise awareness and understanding for people with mental illness. He made no further appearances on Babylon 5 but continued to support the show and appeared at conventions and signing events until his retirement from public appearances in 2000.

On September 28, 2012, Straczynski posted that O'Hare had had a heart attack in New York City five days earlier and had remained in a coma until his death that day.[48] Eight months later, Straczynski revealed the circumstances of O'Hare's departure from Babylon 5 at a presentation about the series at the Phoenix Comicon.

[chasil]

Claudia Christian, who played Susan Ivanova, is also well known for her documentary on alcohol addiction.

https://m.youtube.com/watch?v=crYU4xT1aRI

[TiredOfLife]

It would be easier to list b5 actors without drug or alcohol issues.

[gspetr]

You should delete the spoilers. O'Hare's personal history is important, but the part of the comment about his chronological appearances in the show is not.

[account42]

Eh, being mentally prepared for his sudden departure in Season 2 is not the worst thing. This isn't something he writers intended as a plot twist after all.

[jghn]

Talking about a show that aired 30 years ago isn't "spoilers". Anyone who wanted to not be spoiled has had plenty of time to go rectify that situation by now.

[TiredOfLife]

Could you list more spoilers!?

[chasil]

If you want to know something about the series, then ask.

I will upvote you now.

Edit: Vir waves.

[largbae]

The Vorlons are really a_____!

[2muchcoffeeman]

This is the first loony conspiracy theory I’ve seen posted on HN