Mozilla Newsgroups Message Cancellation Policy
The support newsgroups are monitored by a small group of technical support community members. If they agree that someone is regularly off-topic or repeatedly violates the etiquette document in other ways, they will warn them by private email (or in the newsgroup if the email address cannot be determined). If they later agree that the behaviour has not changed, they will notify the person by email (or newsgroup post, as above) and then start to cancel any and all infringing posts from that person, without warning or comment.
At least the first time round, an emailed assurance of reformation, plus a practical demonstration of one month in length (where the group feels the need to cancel no or very few posts), resets the process.
Currently, no non-spam messages are cancelled in other Mozilla newsgroups.