For those people, Twitter offer recourse. Prosser directed us to this help center policy page "How to Contact Twitter About a Deceased User." A verified immediate family member or a person authorized to act on the behalf of the estate can have the account deactivated. It's a pretty arduous process—much more so than Facebook's memorialization feature: Twitter asks for a death certificate, a copy of a government ID from the person making the request, and a signed and notarized statement with contact information, the request, and a link or copy of the obituary.
It's a lot to go through for a grieving relative. And it might prove easier to avoid the Internet altogether. It's also an all-or-nothing proposition: Some people might want to keep the account active as a memorial, but Twitter only takes requests to remove entire accounts not individual tweets.
Facebook gives the grieving an in between option, allowing family members to "memorialize" an account. That keeps the account activated, while protecting the privacy of the user by making the it inaccessible even with the correct password. It also removes certain features, such as personal contact information and groups. Friends can still see photos and write on the person's wall, however. Twitter does not have anything like that. Friends and family keep a Twitter handle alive at their own risk. Or they kill it and lose all the writings of their loved one along with it.
Twitter's policies on suicide are aimed at preventing them in the first place. Prosser first directed The Atlantic Wire to this "Suicidal and Self-Harm Content on Twitter" policy page. Nothing there speaks to suicide notes. But, if notified about writings that could turn into death notes, it will let the tweeter know that an anonymous someone who cares about them notified Twitter and send along resources. It will also encourage this person to seek help.