So what is the point of this feature if somebody can "fix it" just by downgrading to a slightly lower version ?
Downgrading does not "fix" it. The earlier version would broadcast the transaction, and then it would (most likely) either sit in the network with 0 confirmations for half a day or sit on your machine with 0 confirmations for a few hours, until it aged enough to graduate from the 'very low priority' category.
The rule of thumb is 1 BTC you just received needs 144 confirmations (1 day) before it is considered 'normal priority.' 10 bitcoins requires 1/10'th that-- 15 confirmations would do it.
Given the recent rise in bitcoin value, I think it makes sense to modify that formula so 1 BTC takes (perhaps) 10 confirmations to be considered 'not likely to be spam'.