There is a bug with wm-bot's @seen command when the person was last seen changing their nick. Example:
[17:41] <MajoraWP> @seen UYScuti
[17:41] <wm-bot> MajoraWP: Last time I saw UYScuti they were changing the nickname to , but is no longer in channel #wikipedia-en-help at 3/28/2016 5:54:59 PM (9d3h46m6s ago)
It seems to not be saving the nick change and if they are no longer there shouldn't it say that they were last seen quitting?