Efforts are being made to confirm their identities before they potentially face claims for damages, a judge was told.
Lawyers want to issue proceedings against some of those who posted comments and the administrator of the sites on the social networking giant.
Facebook removed two pages last month after the man's legal team secured a court order.
The pages, Loyalists against Short Strand and Loyalist Peaceful Protests Updater, had provided information on street protests being held across Northern Ireland.
Demonstrations have continued since the decision in December to restrict the flying of the Union flag at Belfast City Hall.
More than 100 police officers have been injured in rioting which has erupted after the protests.
The man allegedly targeted on the pages, referred to only as J18 in High Court proceedings, was granted an emergency injunction against Facebook due to the perceived gravity of the threat.
In court on Tuesday, his barrister revealed that the names of some of those who posted on the pages have been obtained.
"We would seek an injunction against these individuals to prevent any further harassment and possibly damages in respect of the plaintiff," he said.
Basic subscriber information is being sought from Facebook Ireland Ltd in order to confirm identification of those who may be joined as defendants in the case.
Mr Justice McCloskey was told four people are on their list.
The judge directed that the company should provide the information sought within seven days.
He also extended the order prohibiting the contentious pages from appearing on the site.
"The reason for that is the plaintiff is plainly in need of the protection which the order provides, having regard to the evidence which establishes a very significant threat to his personal safety and security," Mr Justice McCloskey explained.
He added, however, that the situation will be reviewed again later this month.
"One of the themes of all of these cases has got to be that these orders will not remain in existence indefinitely but will have to be justified at appropriate intervals," he said.
"The justification for this order is plainly established at the moment."