Considering that my normal account was permanently slowed and is apparently unable to post more than once an hour due to this thread, I'd say "hiding" is useful if one wants to express an unpopular opinion on HN, merely to retain the functionality of his normal account.
That's the system working as intended. This site isn't meant to be about rapid back-n-forth banter or quick retorts and small points.
If after an hour, what you meant to say isn't worth saying then it's clear it isn't worth having on the site.