mIRC cannot join channels when you double click them with "-" or "_" in the names.
How to replicate.
Connect to any server (I used freenode)
Enter this code in the status window.
//echo -a #example
//echo -a #example-bug
//echo -a #example_bug
Double click #example - this will open a window
Double click #example-bug - this will take you to the #example channel window - without sending the "join #example-bug" to the IRCd
Double click #example_bug - this will take you to the #example channel window - without sending the "join #example_bug" to the IRCd
Now, close out of the #example channel. (Should now only have a server status window opened)
This is where it gets interesting:
Double click #example-bug - this will open a channel window
Double click #example_bug - this will open a channel window
Double click #example - this will open a channel window
Also, channels are not click-able after the "-" or "_" so I think this is related to
URL parsing broken? This bug does not exist in 7.22