So, how long after someone threatens to sue you does it happen?
Will a forum just hand over your IP?
Will they hand over your IP of every message you submitted, or just one?
How long do you have to retract your post?
Once they get your IP how long does it take to sue you, etc?
If you post from behind a proxy,(tor) how does that effect things?
If you posted from behind a proxy from most posts, but from your own real one how does that effect things?
A threat is only a threat, take it with a grain of salt. If a certain TTI program had followed through on their threats to sue me for slander and trade interference, I wouldn't be able to answer you. Fornits won't hand over a damn thing without being subpoenaed, Ginger's got your back there. Unless legal papers have been filed, there's nothing to stop you from editing your posts. The plaintiff may try to use that against you, but a retraction is a retraction - you removed the "offensive" material without being ordered to do so, which makes you look better in the eyes of the Court.
If you're well-proxied, the effect is like a monkey wrench being hurled into the grinding gears of the evidence discovery machine. Psy has pointed out that even the Feds can't track down a TOR proxied poster.
You could be accountable for the un-proxied posts. Doubt it, though, especially considering that all the posts about the plaintiff would be reviewed and they may look like assholes in the end.
This threat - is it for libel, defamation, or what? If you've written nothing but the truth, I wouldn't let the sword rattling and empty threats keep you up nights. Most people run for the hills when faced with the prospect of a lawsuit and that's why people threaten them so often. Stick to your guns if you've been telling the truth.
Check some legal sites like Westlaw.