At the moment mIRC has the following behavior when you connect to a server and it starts to auto join channels.

Example :

When you join 15 channels on start and you try to start typing in the 3rd channel. It just continues opening channels and makes them active. This results on your line of text being typed over the 12 left over channels in bit and pieces.

Would be nice if there is a function to stop this behavior so that when you start typing in 3rd channel it just opens the remaining 12 as none active windows ( aka on the background until you select them )

Sometimes you just want to start of typing straight away in one channel and its quite annoying that it keeps switching the active channels while you do that.