Santa Cruz Indymedia currently uses a codebase called DadaIMC and allows users the ability login to set personal preferences and edit your own posts. Editing can be very helpful if you made a typo, forgot to mark your post as HTML, or something like that....
(but, like most things, the ability to edit your own posts can be abused. as far as i know, only IMCs that run on Dada allow users a personal login.)

User Login

IMC logins require that your browser accept cookies from this site.

Enter your username and password to access your preferences and editable items. If you do not have a username and password, you may create a new account.

The login is located in the left column, just above the info library