You can see people with invisibility on, if you have particles on. Although it's not as easily visible as the one presented here.
As far as I know, you can change the chat length (limit) in server.properties. Although I might've misunderstood the problem.
Oh okay. Ill add this to the bukkit team then.
Caster And
You can see people with invisibility on, if you have particles on. Although it's not as easily visible as the one presented here.