Here a little script you can use to generate user accounts if you're running with AuthMode=Registered:
#!/bin/bash
BITLBEE_BIN=/usr/sbin/bitlbee
echo -n 'Username: '
read user
echo -n 'Password: '
read -s pwd; echo
echo -n 'Repeat password: '
read -s pwd2; echo
if [ "$pwd" != "$pwd2" ]; then
echo "Passwords don't match." >&2
exit 1
fi
hash=$($BITLBEE_BIN -x hash "$pwd")
echo "<user nick='$user' password='$hash' version='1'/>"