I don't think this information should be prohibited from being posted, nor do I think that the access of such information should be restricted to certain user groups. As the disclosure (or threat of disclosure) of such personal information gives an incentive to (potential) scammers from attempting to steal from others.
There is really no such thing as "main" account, therefore the prohibiting of the release of personal information from a "sockpuppet" account would be unenforceable. However I do think that an incorrect dox (that is the result of doing little/no due diligence to confirm it's accuracy and/or other gross negligence), or a dox of someone who there is not significant evidence against that they have stolen significant amounts of money (or have stolen any amounts of money from the person posting the dox) should be considered to be causing "serious trouble" and they and their alts should receive negative trust so others should be warned against trusting them with potentially sensitive information.
Regarding themos's dox: I do think that theymos does have the right to protect his privacy. I don't see any major issue with theymos using some kind of automation/scrypt to prevent his personal information from being posted as this is little different from him using the same criteria manually to delete posts (this is assuming that the automation/scrypt does not count towards any page counts for advertising purposes).
If you were to get scammed by the owner of a website/forum, then it would probably not be a good use of resources to post the personal information of such owner on that forum, and I do not see how bitcointalk is any different. Also, if you are going to trust the owner of the forum enough to conduct business on such forum, then to an extent, you are trusting them enough to not delete any accusation/claim of wrong doing that may popup. It is my understanding that there are a few accusations against theymos regarding, among other things his use of donated forum funds, however AFAICT these accusations lack any substantial merit. I have also seen, in this very thread instructions on how to find theymos's dox that are inaccurate (that lack any merit) that have been allowed to remain, however I have also seen instructions that might have lead to a more accurate dox be deleted.
I don't think it is a good policy to ban people simply for posting theymos's dox, or posting a link to where to find his dox. The reason for this is because it appears to be socially acceptable to post personal information and those that post it may not know any better (maybe a warning would be more appropriate for a 1st offense). Also, it would not be unreasonable for someone to stumble upon theymos's dox and someone may genuinely post it out of curiosity to see if it is accurate.
There appear to be allegations that some people are banned if they mention that people are banned for posting theymos's dox (however the credibility behind these allegations is unknown). I think if this is the current policy, then it should certainly be revisited and will only make the forum appear less trustworthy if revealed to be true and such policy is not reversed. There is a lot of inaccurate information posted by a number of people, some with good intentions and some with malicious intentions, so I do not see any reason for banning those that make this kind of statements, regardless of the truth behind such statements.