A suspended user logs in with a new account. The system seems to detect the sockpuppet, and merges the accounts. But while the new account is merged into the existing one, the user seems to be able to login with his old account, despite that it's suspended.
Let me slightly adjust your scenario to match what happens a bit better.
- A suspended user creates a new account to bypass the suspension (this is against the rules)
- The suspended user participates on the site, asking and answering questions with their new account.
- A moderator notices that the new account behaves/looks a lot like the old one.
- The moderator merges the new account with the suspended account, and the user is effectively suspended again.
- The ownership of the questions, answers, and comments are transferred from the new user account to the suspended user account.
This has the appearance that the user was able to participate on the site despite the suspension, which causes confusion. The problem is that there are a few StackExchange philosophies that make dealing with malicious users a bit more difficult.
- It should be easy to participate on any SE site, so it needs to be easy to make a user account. Just prove that you aren't a robot and you're in (practically).
- User generated content is valuable, and should not be deleted if it could be beneficial to the site. Even downvoted answers saying "stick a fork in an outlet" are useful because the downvotes show that it is wrong.
- Users have some good in them, and should be given opportunities to correct their issues. Notice that the user in question got a suspension instead of his account being deleted. Deletion is something saved for worst offenders and/or spammers. Once someone's suspension expires, all is forgiven.
The result is that normal actions that may be taken in a traditional forum (bans and deleting posts) are options of last resort. Aside from deleting content, a moderator doesn't have the ability to ban anyone - that's reserved for the developers. That's why the content stays up.
Part of the problem, in my opinion, is that it is difficult for non-moderators to see this struggle and how it is playing out. There are two options that I see that the moderators could take, but neither is a "slam dunk" policy recommendation.
- Delete content created under suspension. This isn't a good response because even bad questions can get good answers, and bad answers can inspire good ones. However, it would give the appearance that all is well.
- Add a comment from a moderator basically stating "This question was asked by a sock puppet account. The account has been merged with the original parent account." This provides a visible indicator to regular users that action has been taken. However, this leaves comments that would probably remain after the suspension is lifted, and gives more attention to an attention-seeking personality.
In summary, there aren't any great ways for a moderator to notify the community what is happening in this situation. Understand that the issue is being actively monitored, and the developers can act in the event that things get worse.
This still shouldn't happen though - puppet accounts are forbidden.
The same problem happened on SO, and was reported here: Suspended user creating new accounts. Jeff Atwood says that IP blocks are used for users that do this.
According to the article on timed suspension (emphasis mine):
Depending on the severity of the problem behavior — and at the complete discretion of the moderator — your account will be placed in timed suspension for anywhere from 1 to 365 days. That means:
- Your account will be locked at 1 reputation.
- Your user page will have a visual indication that you are in timed suspension, and for how long.
- You will be unable to vote, ask, answer, or comment.
The workaround that stevenvh (and others) noticed serves to violate the third point. The system merged the "puppet account" with the main account, but it should have enforced the restrictions on voting, asking, etc.
It is just giving the answers of the sock-puppet account to the original account. This means that those answers are tied to the original account and looks like they posted answers after being suspended. This is by design as the user still is unable to accrue any rights on site.