It is actually useful for links which end by a parenthesis (often Wikipedia links), as the ending parenthesis isn't kept in the link (to avoid problems when posting a link between parenthesis)

Additional existing tags :

[pic=xyz] (previously "thumb" instead of "pic") to display a clickable thumbnail image of another vehicle, where xyz is the number of that other vehicle.
or [fullpic=xyz] for the full pic instead of a thumbnail (should be used only for small pics, as it is suggested by the site only for these)

[*] to display the yellow star used for role ratings

[flag=xy] to display a country flag, where xy is the two-letter country code