This is a bad idea. Hear me out:

You click on a link to lemmy.world to a post that has hundreds of comments. Instead, you get redirected to my.instance where this community is not federated. The post is immediately federated and loads, and you see the post on your home instance.

But no comments. No future comments, nothing.

A better method would be to have just “action” links go to your home instance. I.E. up vote, comment, save, etc.