Libellous comments

One of the topics over at the WFA has shifted (as does almost every thread anywhere) and as a result Fran posted the following:

Some of the comments about John Campion have been pretty libellous and it is Tav, as the site host, who would be legally responsible for all your comments! 

So how does that work? First I need to add the obligatory "I Am Not A Lawyer". Looking at cases where this has arisen the main point used seems to be the difference between passive and active participation.

If I allow anyone to comment and leave all and every such item unchanged, intact and visible, basically doing nothing to them, I am taking a passive role. As such I claim the same protection afforded to ISPs and the Royal Mail. I can't sue the Royal Mail for delivering a libellous letter.

However where this gets interesting (stupid?) is what happens if someone who thinks they have been libelled in one of these comments contacts me informing me of such. What do I do?

If I leave the potentially offending item up after being informed of it I am tacitly endorsing it and can be sued. However if I take it down I lose my passive role and can be subsequently sued possibly for that very comment or future any comments.

This seems to leave the question of moderation in a flux - you're damned if you do and damned if you don't. However judging by the cases it seems to be the degree of activity involved. If the only active role I take is to remove obvious spam and anything that has been requested for removal I should be safe. However if like Tav I corrected spelling or grammatical errors or de-threaded comments to create new thread that would be a much more active role and he might well fall into the double-damned category.

It's a mess and just another example of how so many of the laws in this country haven't caught up with modern methods.