The default policy for incoming new connections to the firewall generated by this program drops requests rather than rejecting them. As a rule, that works fine. However, Internet Relay Chat (IRC) servers typically send an ident request when a client attempts to connect. If the client does not explicitly reject (or accept) the request, the server waits until it times out. That's obviously a problem.
Selecting this option causes the firewall to create rules to explicitly reject all requests to the ident port (113). It also provides an alternative, commented rule to accept the requests if you wish to experiment with that option. Note that if you are applying this script to a gateway, the stock identd daemon included in most older linux distributions is not sophisticated enough. There are other ident deamons that can. One such is oidentd available at (new tab): http://dev.ojnk.net/.