I somehow agree that these junk accounts are none threatening.
-Most of these junk accounts are definitely Member ranks down to Newbie ranks and Merit selling is impossible. So it's a none threatening for me.


Also, Deleting old and inactive accounts is a bad idea. Deletion of data/accounts will never be the correct way to clean up a mess in a system or community, backing-up is the right term. Deleting old accounts may cause for another account to rise with the same username of the deleted account (unless those deleted account's usernames are still saved somewhere and cannot be used) and might cause impersonating.

Locking old and inactive accounts forever is my suggested idea which means any owner of those accounts who has been inactive for (example more than 3 years) will have no access in their abandoned account. But they can still appeal.