Every day, thousands of people who are consumed by the nation’s opioid epidemic connect on the popular discussion website Reddit.

They swap advice on getting high and offer encouragement to those who have managed to stay clean or are teetering between recovery and relapse. Addicts lament the deaths of fellow users who have suddenly stopped posting. And until last week, buyers and sellers could easily find each other, relying on coded messages that communicated their intent.

Reddit banned the forum, known as opiaterollcall, last week but would not disclose what led to its closing. Another forum to buy opiates quickly sprang up to replace it; Reddit banned that one, too.

They were just small parts of one of the world’s largest online communities. But the dispatches left behind tell a surprisingly intimate story about the tenacity of the crisis, the trajectory of the addicted and Reddit’s role in facilitating access to drugs tied to the mounting toll across America.