you would have needed to so something like...
if ($(#,) isin $1-)
becuase # is a special value that expands to the current channel, so you surround it with $( ,) which is like $eval( ,0) meaning dont evaluate it at all, just leave it as #
however this catches any text with # in it when your an OP and if the nick isnt an OP then it messages the channel.
on @*:TEXT:*#*:#mychannel:{ if ($nick !isop #) { msg $chan No advertise $nick ! } }
now i wasnt sure if you ment an op saying any #etc or just #Jürgenschannel so....
on @*:TEXT:*#*:#mychannel:{ if (($nick !isop #) || (#Jürgenschannel !isin $strip($1-)) { msg $chan No advertise $nick ! } }