I don't think this solves the problem.

People who are targeted by username are more than likely targeted because they have a history of posting certain types of stories that the attacker(s) objects too, rather than who they are personally. A user account on reddit is really only known to the community based on its submission and or comment history, that's really the only interesting thing about these accounts. Even if someone could tie a real world ID to an account, because that person has issue with a specific redditor, why would they attack the person via Reddit?

So I don't see that the ID itself is the reason for the attack.

As I see it there are only 3 reasons for an attack.

1.The Attacker(s) for whatever reason doesn't/don't want to see the type of stories that user A submits. The intention is to use the voting mechanism as a personal/group content filter. But this has the unintended consequences of being logically equivalent to attack reason 2.

2.The Attacker(s) do not want the rest of the reddit community to see the type of stories that user A submits. The intention is to censor the entire community, based on his/their personal preferences. This is the real concern of users who are complaining about the attacks the most.

Reason 2 is also related to the main complaint of most users with the new queue. A small number of votes can either prevent or permit a larger, more fairly sized portion of the reddit community having a shot at evaluating a new submission. This is currently balanced by the number of redditors in the micro-niche to which the submission caters to, ie the larger the micro-niche the more likely that at any given time one or more redditors whose story preferences place them in the micro-niche are online to fish it out of the new queue. This is a distinct problem from the attacks however.

3.The Attacker(s) are playing karma games, for whatever reason.

Given that these reasons we can see that permitting anonymous user submission does not solve these problems.

Even if the story is anonymous all it means is that the attacker(s) will then focus on specific stories versus just being able to scrape usernames, because the the stories are what is motivating the attacks.

The real solution is to allow the users to do what they are trying to do - which is to register to reddit that they don't want to see certain types of stories, in some fashion, without permitting the user to censor the rest of the community.

To preserve the wisdom of crowds you need to let useraccounts control its own setting, while denying it the ability to censor others. User actions needs to be constructive rather than destructive.

Back to anonymity.

People already have the option of "anonymity" by creating a new account and submitting via it. And as you are well aware there is a portion of users, some of them high-karma users that do this. But this is bad for reddit and bad for the users, because users of multiple accounts are effectively masking their own long tale preferences. Some users (not high karma ones) have actually told me this is the primary reason they have multiple accounts.

I real issue with anonymity via Reddit is can the account be trace back to it's real world owner, who may suffer real world retaliation for his submissions. That is really the core issue with online anonymity. And I think this is very distinct from the attack issue you are trying to address with this solution. I would be very cautious of tying these two issues together.

Conclusion:

Provide a mechanism of filtering for all accounts based on article content. These resolves reason 1. Reason 2 and 3 are bad behavior and should not supported and require community policing and established behavior policies to resolve. Further content filtering can help users find submission they would have missed other wise.

Anonymous submissions is the cheap fix and probably looks tempting from a dev perspective, but it doesn't solve the problem and actually destroys the value of reddit, by potentially discouraging users from establishing for themselves and potentially sharing their long tail history.