There are two things that I'd want to mention.
1. @MjnMixael: I perfectly understand your standpoint here. Of course, you want your videos to be yours, since it's important for your work and promotion of your skills. But not everyone has got such worries - I can imagine that some random Freespace player who would be able to make such a playthrough video series wouldn't necessarily need this minor amount of views FSO video get and probably wouldn't even want to bloat his channel with this (or create one especially for this). Like, for example, Colt. Basically, if people want to upload their videos directly to HLP's channel - let them! Of course there should be a mention of who made the videos in descriptions.
2. Youtube allows you to create many different playlists (like most channels there do) and they also let you link to other channels' videos in them. This is pretty often used by content creators who make collab series once in a while, if videos are split between channels both channels include all of them in their playlists. Besides, I'd say that using the "liked videos" playlist is considered not professional at best.