I'm sure we can think of cultures where suicide, in certain instances, is a noble and courageous act. For instance, Japanese feudal culture. There may be examples from courtly love. But there are also many, I would even say most, cases where it is not. I don't think that any "act" itself can necessarily be considered honorable or not without consideration of the person involved and the circumstances.
I think it is very important not to glamorize suicide. There is a real asymmetry in the way many people romanticize the idea. They think, Oh, life isn't worth living, it would be noble and honorable to end it all. But were a friend or loved one to think the same way, they would be horrified. They would spend years wishing they had had just one more conversation with this person they loved, just to understand. Suicide is an extremely strong rejection of others, and can often be something deeply selfish. At the very least, it can say "my pain was so great, you cannot imagine, I could not bear it" and this is hard not to interpret as an accusation.
Philosophically, we could ask, is suicide really courageous? What makes this a hard question is that you do not really experience it. You intend to do something, and if it succeeds, you are unaware of the result. Is an intent courageous? In what sense does one really understand the fact of one's own death?
Usually, in my opinion, the really courageous act is to go on living, to deal with the unhappiness, uncertainty and pain, and to make something of one's remaining time despite it all.