Here's what Sean posted when he locked it:
So the two main points are that it's advertising, and that it's not his own content.
About LPs, I'm pretty sure they're technically not allowed because they more or less count as advertising. I'm going to lock this, but feel free to post them in your signature.
Also, since this is in the showcase forum, it also doesn't count since you didn't make the videos themselves, just the commentary.
Regarding it being advertising...well in a sense, yes, but so's linking to your DeviantArt page in your artwork topic, and there's nothing wrong that that, right? The rule against advertising, as I see it, is to prevent people from just dropping a link to their DeviantArt/Youtube/whatever page telling people to go there and then abandoning the topic. That's not what Shade was doing; he posted links to his previous work, and planned to post links to videos as he made them. I see no reason why this is "advertising" any more than any Showcase post that links to some off-site repository.
Regarding it not being his own content...he plays the game, he records it, he commentates it, he edits it together. How is that not his own content? The game itself isn't his, but his playthrough is his own, and obviously his commentary is his own as well. And we've got topics for game reviews and abridged serieses going which are made up of footage from games and shows, and there doesn't appear to be any problem with them.
So, what am I missing? As far as I can tell there's no reason LPs shouldn't be allowed.