The law of defamation is complex. Rely upon nothing you read here without first taking direct advice on your particular problem. Having said that anyone can be a fully fledged expert on defamation. Neither encourage actions against you, nor, ever, under whatever provocation, begin a libel action.
Defamation protects reputation, no more.
Words are defamatory if they tend to reduce the reputation of the claimant in the minds of right thinking members of the public. Words are frequently both defamatory and true. The claimant must have a reputation which can be damaged. This can limit claims by companies, larger groups, and public authorities in different ways. Sometimes private individuals can have no reputation capable of protection - which is why newspapers can have a field day against somebody who has been convicted of any serious offence.