it is a threat if users jump ship to beehaw from the smaller instances beehaw has blocked. but when I wrote that comment I wasn't aware that lemmy.world is now three times the size of beehaw, at least according to this tally https://github.com/maltfield/awesome-lemmy-instances. that should counterbalance things.

The issue with this is beehaw is large enough that them defederating from other instances is potentially a serious threat to those instances. Social networks are inherently monopolistic because people follow the crowd, and federation is meant to counteract that tendency toward userbase consolidation. Moves like this could be interpreted as an attempt to become the dominant instance, defeating the purpose of the fediverse.