Hi,
Interesting scenario, as you point out the correct broadcast address for your network should be 161.253.235.255
The IP address seen on the ARP request is a usable IP address under your IP addressing scheme, as weird as it may look at first glance 161.253.232.255/22 can be safely assigned as the available IP range is 161.253.232.1/22 to 161.253.235.254/22
A quick explation can be found on:
http://expertanswercenter.techtarget.com/eac/knowledgebaseAnswer/0,295199,sid63_gci1053572,00.html
So, I think there's nothing wrong with your network, and no, ARP requests for the broadcast address are not normal behavior.
Best regards.