I recall there have been a few posters who have cycled accounts to make top-level posts, but I think this declined dramatically after the karma minimum for posting went up. So probably a pretty low-priority, but I agree there is an incentive problem (depending on how attached people are to their accounts).
It came to my attention that when you receive downvotes for your comments, your karma goes negative and you need to "pay back" to be able to post to Discussion or to Main.
Since new users start with zero karma, having negative karma seems to just encourage those with negative karma to create a new account. We don't want to encourage people to create superfluous accounts, do we? Therefore I think LessWrong codebase should be patched so that karma does not go below zero even with lots of downvotes.
What do you think?