RFC 1459 : Internet Relay Chat Protocol, J. Oikarinen, D.Reed.
4.2.3.1 Channel modes
Parameters: <channel> {[+|-]|o|p|s|i|t|n|b|v} [<limit>] [<user>]
[<ban mask>]
The MODE command is provided so that channel operators may change the
characteristics of `their' channel. It is also required that servers
be able to change channel modes so that channel operators may be
created.
The various modes available for channels are as follows:
o - give/take channel operator privileges;
p - private channel flag;
s - secret channel flag;
i - invite-only channel flag;
t - topic settable by channel operator only flag;
n - no messages to channel from clients on the outside;
m - moderated channel;
l - set the user limit to channel;
b - set a ban mask to keep users out;
v - give/take the ability to speak on a moderated channel;
k - set a channel key (password).
While I agree, mIRC should be "dynamic" it should not include functionality for something that is not, "cast in stone", for example; +k and +l have specific "spaces" in /channel, as they are defined in the RFC, I see no reason why +f/j should have the same "treatment" when it was simply dreamed up by some "coding team".
Eamonn.