When the IP address passed to /dns does not resolve to an hostname, /dns reports that it resolved the ip to.. that ip.
[21:39:45] * Dns resolving 2a02:214b:8125:8e00:bc56:8788:2655:52f3
[21:39:45] * Dns resolved 2a02:214b:8125:8e00:bc56:8788:2655:52f3 to 2a02:214b:8125:8e00:bc56:8788:2655:52f3
If this is expected, then the help file should be updated.
Others strange things with /dns (try it on a connected server):
[21:57:28] * /dns: no such user ~westor@Swift-EAD07A2A.dsl.dynv6.forthnet.gr
The help file says that if there is a ., it recognizes it as an hostname and try to resolve, so it shouldn't think it's an user here. Remove both the ~ and the @, and now mIRC try to resolve it as an hostname.
[22:02:34] * Dns unable to resolve address !@..
Basically recognizing email address and trying to resolve the domain, but none of this is documented, so that's a bug as far as I'm concerned.