The current modifier field can be used for:
1) Handling expiring passwords, by allowing a version number etc.
2) Adding a salt
But doing both is difficult with just one field. I have passwords that expire, so have the need to version passwords, and also have extreme paranoia over rainbow tables, and also want to be able to add a salt. So, I'd like a 2nd "modifier" field. What exactly they are labeled is not of great concern to me.
Thanks,
Shawn