get overlayComments() {
      const uniqTargetKeys = new Set();
      return self.comments.filter((comment) => {
        const { regionRef } = comment;

        if (!regionRef) return false;
        if (uniqTargetKeys.has(regionRef.targetKey)) return false;
        uniqTargetKeys.add(regionRef.targetKey);
        return true;
      });
    }
A subset of comments that should be displayed on the overlay.
For now, it uses only the last comment from the group of ones linked to the same target.