You might be focusing on the wrong area here, you are being provided with an opportunity to see some weaknesses in your process.
- works in his own little area of his home directory rather than in the common CVS repository
A simple chat will probably suffice here, the benefits of version control speak for themselves and any "bright" person would likely be enthusiastic about those benefits. However it may also be a good chance to look into alternative version control systems that allow greater ease of use and flexibility (take a look at bzr and git). Better yet, get him involved in the selection process, if he really is a "star" he'll probably have good input and be more vested in its use.
- doesn't document his code
It doesn't sound like documentation is part of your process. People are going to resist having to do extra work and if there isn't a defined process then you're talking about a lot of extra work. Is documentation really needed? If so, is there a process defined for creating it? should you have someone entirely dedicated to it? Should you at least have a tool to facilitate it (maybe something as simple as mediawiki)?
- doesn't comment his code, e.g. 3,500 SLOC of C with no comments and no blank lines to beak things up
Three words: peer code review. Outside of obvious error-catching benefits, this also can provide some peer pressure, which is a strong force and can be a good thing. Wanting to be perceived well by your peers self-generates ownership and quality.
- often overcomplicates things, e.g. uses three shell scripts that call one another to do the work that one simple shell script could do.
Again, peer code review. You mention that management knows about this programmer's deficiencies. Does he? It's rather difficult for people to change and improve if they don't recognize the problems with the way they're doing things.
And, perhaps best of all, by coming up with plans to improve your development process (which will likely improve not only your "star" but everyone else on the team) you can probably earn some gold stars for yourself from management.
