Granted I do see that YT has the same issues. I don't think its easy to manipulate, but all recommendation systems are going to have people trying to manipulate it.
He claimed that creators using the Community tab was disproportionately rewarded by the recommendation algorithm. (Since the community tab was a new feature, YouTube wanted the feature to show up in peoples' feeds; but since few creators were using the community tab, it meant those that did got a big boost). -- IIRC, this evened out once everyone started using the feature.
SpiffingBrit also suggested that copy-pasting many of the trending keywords in comments would help the recommendation algorithm show the video. -- This turned out to be incorrect; but for about a week, most of the comments I saw in a bunch of videos had the same 300 words copied and pasted.
(which is a highly entertaining channel, it's good he's self-aware)