I noticed some time ago that, if an irc operator is searching for a listing of +s channels (secret) mIRC seems to not search for secret channel listings that have non-standard ascii chars in them such as #»»« (Or)
# $+ $chr(187) $+ $chr(187) $+ $chr(171)

//quote list S >300

-> Server: list S >300
-
got numeric 321
-
Listing channels
-
got numeric 322
got numeric 322
got numeric 322
got numeric 323
-
End of /List

I did notice in mIRC help there is no mention of an -s switch in /list However other irc clients irssi xchat (that i tested) have no problem, finding secret channels such as the one above, the behaviour is beginning to become annoying, perhaps you'd like to adjust mIRC to do so.

Tested on undernet Ircu u2.10.12.12

Best regards
Scot

Is 'Hide non-text channels' enabled in Channel List Options (Alt+L)?

well silly me, i missed that entirely.

Thanks Collective