BIND 9 is multithreaded. It's nothing to be afraid of. By the way, if you need to stop or reload the name server, remember to use rndc instead of sending signals to named . BIND 9 doesn't support name checking. Some wouldn't view this as a gotcha since it liberalizes the characters that BIND accepts in domain names, but it's worth noting.
Legal characters are alphanumerics and dash.
BIND 9 doesn't implement name checking, though. You can use any characters you want in domain names, including underscores. You should keep in mind, however, that many resolvers now implement name checking, and may not be able to resolve domain names with weird characters. BIND 9 developers don't hang out in the same old places. In the past, you could expect to find BIND developers hanging out in the bind-users mailing list , which was bidirectionally gatewayed to the Usenet newsgroup comp.protocols.dns.bind .