CJK Unified Ideograph Extension B/C/D are all pretty exotic though. In normal daily use you won't encounter them, because input methods rarely offer them and people simply don't need them. These are important characters, but only a handful of them will ever be used by the average writer of Chinese or Japanese.

I was using some of these (from B and probably C) for very specific purposes at that time, and general support was a long way off in 2009 (although already good on GNU/Linux distributions).