Regardless of the merits of removing some accounts for some definition of 'some', it's seems to me that it was perhaps shortsighted to key on username, rather than say, user homenode id.

If it had been done this way, allowing people to change the usernames (if they chose badly when they first came here, not thinking about haw long they might stay around), and removing un/little- used names from the system would have been a simple process. All write-ups having been keyed to the home node number, would simply stay in the system but would be attributed to user_nnnnnn.

Still, that's beauty of 20/20 vision in hindsight.

Difficult to know without seeing the schema, but (thoroughly tested on a backup DB of course) it doesn't seem that changing things to work this way would be an extraordinarily difficult thing to do.