Last modified: 2014-08-06 10:55:28 UTC
Currently on en.Wiktionary (1.20wmf8) IPv6 addresses are displayed with uppercase hexadecimal digits. For example 2001:0DB8:85A3::8A2E:0370:7334. According to rfc5952, when an IPv6 address is rendered as text it should be in the shortest possible form and use lowercase only.
We probably can't use the abbreviated version; it's a little late to suggest lower case because some IPv6 addresses are already tagged on their userpages (which are in caps; changing the case will not automatically correct the case of those IP userpages).
"It's too late" --> but it's only going to get worse, especially if other sites start using lowercase and we look weirder and weirder. Moving pages is trivial, IMHO we should change over ASAP if it's going to be a future issue.