Instead of creating a separate user_entry table, why not just add IP address users to the user table? (Or in the case of wikis that use CentralAuth, to the extension database tables.)
If we must have a new database table, can the new user_entry table eventually take over all of the _user_text fields (ar_user_text, img_user_text, log_user_text, oi_user_text, fa_user_text, rc_user_text)?
One reason not to put them in the user table is that user has... user-specific things like options and password hashes that do not apply to non-usery things. Another reason is that the idea that 0 id is anon and nonzero is logged in us baked throughout mediawiki and may be hard to remove,
I'm unconvinced that user_entry table is a good idea at all. It just makes things really messy. Although it would be nice to get rid of rev_user_text, it might be more straightforward to keep it around; it doesn't seem like it contributes too heavily to the bloated size of the revision table. .
The furthest I'd be prepared to go would be to make rev_user_text NULL when rev_user is nonzero. This would streamline user renaming among other things.
As MZ notes we have similar *_user_text fields in other tables, and I like the idea of migrating those over too (perhaps later, or perhaps all at once).
Another possibility is to move user_name into a common naming table too, though that might be freakier. :) Related to the titles table idea Jaime has mentioned a few times, in terms of having a common place for common things.
