Antinote never silently overwrites your writing. When a note comes back from iCloud, it is compared three ways: what you have now, what the other device wrote, and the last version both sides agreed on.
Edits to different lines merge automatically. If you changed line 2 on one Mac and line 4 on another — even while one was offline — both edits land in the note on every device, with no conflict and nothing to clean up.
Edits to the same line become a conflict note. If both devices changed the very same line (or one inserted or deleted lines where the other was working), the newest synced version wins in place, and your other version is preserved in full as a new note marked --==SYNC CONFLICT==-- — an "Altiverse" note, placed right after the original. A warning pill points you to it; keep what you want and delete the rest.
Pinned (slotted) notes resolve in place. Slots are permanent, so instead of a separate conflict note, the other version is appended inside the slotted note below a --==SYNC CONFLICT==-- divider. Both versions stay in the slot until you tidy up.
Unsaved keystrokes count: if a synced change arrives while you are mid-sentence, what's in your editor — not just what was last saved — is what gets protected.

When Two Devices Edit the Same Note