Why were those numbers like 3; 14:7 used?
Those are control codes for colors.
How does it actually detect that I've received particularly a PM?
The ? is the part that specifies a PM.
Are you able to copy-paste script code from this page into mIRC script editor without any formatting issues?
The boxes or dashes you see are control code for colors (press ctrl+k to insert it, 0x03). While the character is not usually rendered in browsers it is copied correctly and displays in the script editor - this is not a problem.
