All the communities on lemmy.lukeog.com are mirrors of Reddit boards. lemmy.lukeog.com does not accept posts from Lemmy users – only its bot may post and comment, and its posts and comments are just mirrors of Reddit posts and comments.
This doesn’t seem like a useful way to use Lemmy. It’s more like just a mirror of Reddit, in which case archive.is or web.archive.org would be more useful, in my opinion.
Better not to waste bandwidth and resources on this, in my opinion.
Defederation should be reserved for cases when federation can harm the host instance.
Unless the cost of federation becomes that high, I’d recommend keeping federated.