Re: Totally confused
UK law is pretty simple on this: everyone involved in the process of publishing a defamatory statement to a third-party is technically liable for libel. There is a defence in the schedule to the Defamation Act that exempts, say, ISPs from being liable for libel committed by their users over their networks. The same defence is used by websites that allow unmoderated comments.
So if you want to sue a newspaper for libel, you can sue the writer, the news editor, sub-editor, the revise sub-editor, the production editor, the editor, the publisher and anyone else who participated in the story. Usually, though, you go after the money: the publisher.
Similar goes for websites: the comment poster, the web master, the host, etc. Having Wikipedia based in the UK makes it easier for a claimant to pin down those in the chain - but not having a server in the UK doesn't make it immune to proceedings in England, it just makes it harder to get someone into court.
And as for Twitter, that was a criminal investigation by the police into threats made over electronic communications. Libel is a civil matter and totally different.
PS: For those suggesting adding "I think" to a sentence makes it immune to action, consider the case of a music concert reviewer who was successfully sued for an opinion that wasn't substantially based on the truth.
C.