We have been stripping trailing 'garbage' like trailing underscores since
commit cc7042fa, which solved getting highlights for the regular nick
after reconnecting as nick+'_'. However the nick is also used frequently
to convey status - 'nick-away', 'nick|bbl', 'nick_office' - which is not
covered by the current approach. To include those variants in highlighting,
match up to the first non-alphanumeric character (rather than the last
alphanumeric one).

https://bugzilla.gnome.org/show_bug.cgi?id=755133