Double-arrows let you signify that the tag is different with no extra effort because it's just an extra tap where your finger is already positioned. It also ha

Double-arrows let you signify that the tag is different with no extra effort because it's just an extra tap where your finger is already positioned. It also has a right directionality to imply that it has scope until the end of the line. Triple-arrow is the same idea, but uses the convention that triple-characters are common for delineating multi-line blocks.