The primary purpose of /ignore is to block interaction when you feel harassed or offended by another player. This is almost invariably a negative reaction to a PLAYER, and not the CHARACTERS you and they happen to be logged into at the moment, which is usually completely irrelevant.
Blizzard's standard answer for dealing with in-game harassment between players is "use /ignore" (eg http://us.battle.net/wow/en/forum/topic/10127512817?page=2#22), but that doesn't work when one or both players have 10+ alts and the harassment is determined or persistent. A harassed player should not need to manually track down every alt of the harassing player to individually ignore (adding to a very limited-length list), especially since a determined attacker can create new alts at a whim. Nor should they need to manually copy this ignore list to every toon they play. Yes you can submit a GM ticket for serious cases of harassment, but in my experience enforcement of such cases basically amounts no more than a slap on the wrist at best (nor should customer service be expected to sort out personal conflicts in cases that are not clear-cut violations of the law).
Give us the tools to properly block harassment ourselves: Ignore means this PLAYER never wants to hear from that PLAYER again. /ignore should be account-wide both ways. It should ignore all the characters of the offending account for all the characters on my account. Anything less greatly weakens the effectiveness of the deterrent and leaves no suitable recourse.
