Yes there are 510 usable hosts in a /23. Classes are really meaningless once you break the /8, /16 or /24 boundry. Example 10.0.0.0/23 is technically a class "A" address, it still contains 510 hosts. 172.16.0.0/23 is technically a class "B" address, it still contains 510 hosts. 192.168.0.0/23 is technically a class "C" address, it still contains 510 hosts.
When using a /23 mask there is a very quick shortcut you can use. If the 3rd octet is an even number it immeadiately tells you it contains the network address and the rest are valid hosts. If the 3rd octet is an odd number it immeadiately tells you it contains all hosts and the broadcast address.
18.104.22.168 is a network address
22.214.171.124 is a valid host, it belongs to the 126.96.36.199/23 network.
188.8.131.52 is the broadcast address for the 184.108.40.206/23 network
220.127.116.11 is a valid host on the 18.104.22.168/23 network
22.214.171.124 is a network address
126.96.36.199 is a valid host on the 188.8.131.52/23 network