Alt detection is now live - check out an example from my handsome warrior:http://www.guildox.com/wow/toon/us/Barthilas/Polarbeard
It can be disabled by going into the game, selecting Interface/Display and then checking the "Display Only Character Achievements to Others".
Note that you must actively log into your alts in the game for this detection to work - this will ensure your alt's achievement points are updated to match all of your other toons.
There may be some alts that don't get detected (after you log in and out of the game and then hit the "update" button). Let us know if you find some that are not coming up and we will investigate. There are some limitations to the system but let's see how it goes.