This is too primitive of a solution, and just furthers the behavior of “here at Lemmy, message delivery doesn’t matter, and we do not notify senders when delivery fails”. Auto-defederate based on a single http connect attempt just furthers the design issues of treating Lemmy to Lemmy replication of entire communities as a real-time task that the code is doing so poorly performing without a separate MTA service.

It uses REQWEST_TIMEOUT, which I have pointed out that the value of 10 seconds is likely not suitable given how slow busy Lemmy servers are running. I suspect timeouts are causing retries, making servers even busier. And that is why replication of comments is often delayed or failing entirely.