I'm actually in a somewhat interesting position when it comes to this. I already have someone who knows I am here on the site, my partner/significant other of nine years. She has some misgivings, but even though she's far from comfortable with me being here, she knows I'm not suicidal, and never have been. I came here to commiserate with and try to be supportive of people who have suffered some of the same traumas and mental health conditions as I have, and much worse besides. Because I'm not seeking a way out, she trusts me when I tell her she has no reason to worry.
She still has misgivings though, like I said. For starters, even though I've never been suicidal, I have been severely depressed for most of my life, and remain so. It wouldn't be a terribly large leap for me to cross over into SI, especially when exposed to the kinds of emotions and human suffering one would expect to see in a place like this. We both understand that, and she is understandably wary of it.
But there's also my family to consider, my mom and my brother. They do not know I'm here, and I'm not sure I'm comfortable with telling them. For one thing, they don't trust me the same way my partner does. This is at least partly my own fault: I've never been open with anyone the same way I've been with my partner. I've always been the type to close myself off, so they don't really have a window into my inner world and how I feel. Moreover, they know how severely depressed I've been for most of my life, and even though I've never been suicidal, they don't know that. Nor do I think they would really believe it if I tried to tell them. At the very least, I know that me potentially being suicidal is a concern of theirs, and that seeing me active on this site would most likely add fuel to that suspicion. And I honestly have no idea where they'd stand on the ethical ramifications of me being here, because I don't know (and haven't asked about) either of their views on issues such as right to die.
Needless to say, if anyone in my family caught me on here or knew I was active, it'd be an...awkward conversation. I'd like to think I'd stand my ground, though, and be honest about my intentions. I wouldn't have come in the first place if I wasn't willing to own up to it in the event push comes to shove.