Complex sentence: Advocacy of any sort within articles is prohibited by our policies on and what, and paid advocacy is regarded as an especially egregious form--the Wikimedia Foundation regards it as a "black hat" practice.
Split into simpler sentences: Advocacy of any sort within articles is prohibited by our policies on and what, and paid advocacy is regarded as an especially egregious form of advocacy. The Wikimedia Foundation regards it as a "black hat" practice.