Tiny federates with huge - nothing happens, they just exchange metadata. Dancer@tiny subs to something on huge - now you have one community, with a lot of updates, coming at tiny. Maybe it drops some. Still not an issue
Hugo@huge subs to something on tiny - now something@tiny is cached on huge, still not a problem.
Now something@tiny is in the feed on huge. A million people comment. This is a problem… For huge mostly. Over at little, people are commenting on something@tiny. They might see doubled up comments or orphaned comments, but mostly they just don’t see most of the stuff from huge
So generally, it’s not an issue. In certain situations, there will be hiccups, but it will keep chugging along