Libel is the publishing of statements that have a negative effect on someone's life, which usually means their reputation. The exact rules for what constitutes "publishing", "negative effect" and "reputation" vary from place to place. Threatening to file libel actions creates so-called libel chill - a tactic which varies in effectiveness depending on strength of local libel laws:
In some places, notably Ontario, Canada, libel laws are so loose that even just telling the truth can still leave one open to libel charges. An example was Garth Drabinsky, founder of Livent Productions, whose accounting was called "questionable" by a stock market analyst - Drabinsky sued in Ontario, and, successfully shut up the critics - putting a "chill" on them all. Years later, the head of the US Securities and Exchange commission called the same accounting "smoke and mirrors to put any of his productions to shame" in the course of a fraud probe (which Drabinsky evaded by staying in Ontario and not visiting the US to face the charges). So clearly, true statements on the record were successfully hidden using Ontario's too-liberal libel laws... and even saying true things about anyone who can sue in Ontario is dangerous. (People come from all over the world to sue in Ontario, actually, and as a result it has become the home of some rather notorious fraud artists...)
Some habits on a large public wiki are extremely dangerous as they lead almost naturally to libel by some definition: echo chamber tactics by definition pass around untrue statements which some people believe and then pass on as if they were fact. If there is even one IP block in place it is effectively a "published" statement, as not everyone can edit to correct it. Additionally if editing User talk pages is forbidden or subject to revert, then, such statements on such pages can be considered published - although depending on the rules they may be published by the User not the operator. A controversial project like Consumerium that has a real economic effect via the Consumerium buying signal will attract all kinds of legal attention, some of which can become legal problems quite easily if pre-emptive effort is not made to design a governance system to avoid it.
A troll-friendly wiki for instance is almost naturally immune to libel actions, as, there are few or no block IPs in place, and all of them for simple vandalism, with no witch hunts, meaning, even an unpopular user can find another IP number and correct false statements made about them or their activities. If an active effort is made to out or otherwise identify recurring users, then, it is clear that the returning user is not obligated to "try to correct" the false or libellous statements or at least not more than once... especially if this subjects them to further abuse or blocks the IPs of other users or groups or institutions who may share their views or not. So failing to be troll-friendly actually causes this legal problem.