I have never been suicidal. But I think that if one has those thoughts and feelings it it essential to be able to talk about the in therapy, also to contact your T when you have this feeling...what is the purpose of therapy then? If you can't talk about something as serious as wanting to stop living.

I also understand some people, with specific personality disordes my use the suicide threat just to get their therapist attention. I guess in that case the T is trying to set some boundries/limits as to prevent acting out.(by refusing to handle suicidal crises) But this requires a very well trained T...to be able to asses the postential danger.
I guess suicidal thought are really hard to handle for both patient and T.