It is really common on here now to see an accusation that what an MNer said is libellous. It rarely is.
Libel is not a criminal offence, it is a civil wrong. Someone has to take you to court.
Libel refers to damaging someone's reputation and character and is based on stating as fact, things that are untrue.
So if I said someone famous who is known to be in a happy marriage was having an affair with someone else, and that was false and I said it maliciously, it would probably be potentially libellous i.e. that famous person could take me to court. Although unless you have an online following, that is very unlikely to happen.
But if I said the famous person was sleazy and I would not trust them, they seem the kind to pretend to have a happy marriage in public while having multiple affairs, that is unlikely to be libellous. It is my opinion and is not presented as a fact. It is the second kind of statement that some MNers keep saying is libellous.
You can say legally that you consider a named politician or famous person to be untrustworthy, sleazy, a bit thick, etc. It is opinion.
So please stop telling people that what they have said is libellous. The only potentially libellous comments I have ever seen on MN (rare) are deleted when reported. The matter is just an opinion that you may or may not agree with.