My (old) mud had similar problems. What they instituted was an
account system. You create an account and all of your characters are
listed under the umbrella of this name.

The role of this account is to allow you to reap benefits for
consistantly good RP. The account benefits they allow are:

*add a last name during creation
*select traits that shape your character's personality (at the expense of trains)
--Pack Horse - able to carry more weight
--Cowardly - easier to flee from combat
--Eagle-eyed - increases the max scan distance by 1 room
*select special races (currently only one)
*flag yourself as a follower of a god from creation (only visible to the IMMs, not other players)
*recieve powers based on the god you selected to follow
*create a family heirloom that grows in power as you rank (not rot_death)

(they're listed in terms of # of points required: least to most)

I'm unsure what measures they use to stop you from making several
accounts, but I'm sure there are some.

This would help in determining which roles a person typically plays,
which characters they have played previously, any notes IMMs care to
flag the account with, and any other trends that might present
themseleves during the entirity of their career here.

Hope this is helpful.

-aunes