duplicates or otherwise non engaging accounts.

Yeah, I wouldn't be surprised if duplicate accounts are a part of this but that seems like it would be a natural part of growing pains for lemmy. The way the fediverse is built would suggest that people who are serious about long-term participation may bounce around a bit. For example, I joined in June but in that time I still managed to test out two other instances before settling on a third that seemed to strike the ideal balance between admin policies and reliable uptime to suit my needs.