I can understand the need to keep accounts accurate etc, so it seems mroe than fair to remove "dead users".
I think maybe a generic "Guest Account" be created by Admin, and new users can login as GUEST to lurk/watch/read whatever they like, with no POST access.
This will greatly reduce the number of curious members who signup and never return.
I understand many people like to read & learn from forums without ever needing to participate, nothing wrong with that, and there's no need to create dead-user accounts.
Users who finally decide to join in, can then choose to create a new account.
I used to run a BBS (Bulletin Board Service) way before internet was in your homes, so i know the frustration of dead-user accounts
Hope this helps?
MM.