This paper gives the kinds of complements: noun clauses which function as subject and object; tenseless embedded sentence; noun clauses governed by prepositions.
Similar in principle to the enclosing of parenthetic expressions between commas is the setting off by commas of phrases or dependent clauses preceding or following the main clause of a sentence.
There's more threat of backbiting and there are only human resources with no defined pet clause to settle ruff reports and hissy fits that others find un-meow-sing.