CAPAB is an irc extension of ircd hybrid which allows to request a extension for a link. If either end don't support a capability (or CAPAB command at all) it is ignored. CAPABility ZIP allows for data compression (the server must be compiled with ZIP_LINKS).
Many uses of irc.wikimedia.org involve specific software, which are likely to add support for it (as opposed to normal irc clients), and given the amount of messages on that server, compression would make a difference on user bandwidth.
However, use of compression is not allowed for clients.
I'd have filled this bug time ago, but after querying about it, thought the code wasn't available any more. So _please_ put it on svn (either full or as a diff)
Version: unspecified
Severity: enhancement