You can flag a post if you are using the website through a browser (not sure you can through an app). Just click the little flag in the upper right of a post and choose the reason you are flagging it.

Not aware of a way to flag a user ... is this user posting inappropriately in a forum, or private messaging you inappropriately? If the former, I'd just flag. If the latter ... not sure what your options are.

yes he posted inappropriately. someone else reported it so now its gone.