phpBB3 has a stricter username system where it is strict on the characters that can be allowed as a username. This means that when a certain name is already in the database, another username with a similar or same looking username cannot be used. These similar or same looking usernames were allowed in the previous database because they had different letters, yet looked the same, so phpBB2 would think they were different usernames. However, in the new system, regardless of which special characters were used, if a special character is used to make a username look like an existing username, then it’s not allowed.
Such a system is required to prevent imposers and spammers from trying to bypass restrictions put in place by our moderators.
Because the current phpBB2 system is different from the improved phpBB3 system, there are potentially usernames in the existing database that will have collisions in phpBB3. These are a small number of users (less than 300), but a number of our userbase, nonetheless. Those who have no posts will be automatically deleted. However, those who have posts, will be notified by one of our moderators and provided a period where they can reply with an alternate username. On balance, we believe that this policy for these users is fair and most efficient for the conversion.
We hope that this doesn’t inconvenience anyone too much.