I don't have the port 113 forwarded in my router.
Investigating a bit:
-the identd server feature isn't working, even if I change the port number, I don't use that feature but I'm almost certain it worked in the past, perhaps in a different (recent, 7.2x) version of mIRC.
-typing /socklisten -p test 8002, the 'upnp port forwarded' program automatically detect the change whereas is doesn't find anything when using the identd server feature, so there seems to be a difference in how the identd server feature handles upnp, compared to /socklisten -p.
The problem seems to be ipv6 related, that's the only difference there is betweeen /socklisten -p and identd, enabling the identd server results in this in netstat:
Proto Local Address Foreign Address State
TCP 0.0.0.0:113 Wims-PC:0 LISTENING
...
TCP [::]:113 Wims-PC:0 LISTENING
When using /socklisten -p, obviously the ipv6 line ([::]:113) doesn't appear.