I've always had a policy of no personal attacks both in articles and comments. I've just had two comments, the second one in particular which made some valid (but easily answerable and previously answered) points, but couldn't post them as they both contained personal attacks on a previous poster.
I've no idea why anyone would resort to this, we are all working towards the same thing.
I am unable to edit comments so if a comment does include a personal (or indeed general) attack or insult it HAS to be rejected. You are wasting your time if you send a comment but also feel the need to attack a person, people or an organisation, the comment will not be seen by anybody.
It is also a courtesy to at least use a nickname or first name when posting comments, so other posters get to know you. Whilst I will of course permit anomynous posts (not all of us have Google identities) I think that what we are doing is so important and historic that we really should ALL identify ourselves when commenting, even if just for the historical record!