Doing a quick search turned up these results:

result 1 - result 2

Personally, I really don't use mirc much anymore, but I never saw the need for strike through text. When I was using mirc all the time, I wanted ^S to be used for something else (the symbol font Pirch used), but strike thru, is nothing more than a visual thing and doesn't add to the program at all. It's not to say it WONT be done, I just wouldnt support the addition of strike thru - I'd rather see other things added than more font styles.

Those who fail history are doomed to repeat it