Is there a word or term commonly used to describe the act of stating the obvious (or a person who continually does so)?
He constantly states the obvious, he is such a __.
She is always ___ing.
As a somewhat insulting noun, "Captain obvious" can be used for someone who is always stating the obvious.
Prolixity can be used to describe someone who says too much. This may be applicable in some cases.
In addition, Logorrhoea is a term with a similar meaning to prolixity although again the primary meaning is simply too much vs. stating the obvious.