There's probably far more, but these are the ones that I had in my notes, which I noticed mainly based on Q/A they posted:
- Have I just missed a lot of unregistered users with IDs between 2000-3600 or is there some possible reason why we've had such a high density of unregistered users between ID 3600 and 3999? There have been bugs for user registrations in this network in the past.
1 [This user](https://mattermodeling.stackexchange.com/users/4169/ramesh-kumar) asked a follow-up question, which in it's original form looks like it was from the same person. 2 It's just a new account made by a user on Chem.SE who had their question migrated to MMSE: https://mattermodeling.stackexchange.com/a/6596/5 (you need access to moderator tools to see this link).