There may be a small tradeoff in convenience, but those kinds of walled gardens aren’t discoverable on the open Web and don’t get as much traffic. I think that memory sports won’t grow quickly and be able to reach the mainstream if people can’t find the information by searching in Google.
It’s already possible to install the forum on mobile phones (with chat-like notifications), but there should probably be some more real-time features.
(For example, you can subscribe to all posts in the Memory League section and get push notifications on your desktop and mobile phone for each new post.)