>> I suspect, without proof, that this is because a large segment of the global population watches music videos and variety show clips on YouTube, over and over

>> I suspect, without proof, that this is because a large segment of the global population watches music videos and variety show clips on YouTube, over and over on repeat. That's a great point, and could very well explain showing me videos I've already watched. Fixing my other two complaints would require keeping track of how many times a video has been recommended, and consulting my watch later list when building the recommendations list. It seems safe to assume YT is not unaware of these possibilities, so they must have reasons for not adding these signals in.