Note A (id: a1)

├── Reply 1 (id: r1, parent: a1, root: a1, depth: 1)

│ └── Reply 1.1 (id: r2, parent: r1, root: a1, depth: 2)

│ └── Reply 1.1.1 (id: r3, parent: r2, root: a1, depth: 3)

├── Reply 2 (id: r4, parent: a1, root: a1, depth: 1)