These characters are called non printable character, they are not meant to be displayed/printed, in the past we were basically lucky to get them rendered in some ways that wasn't a pain.
It never was a good idea to use these character as it is in scripts, a terrible idea in fact.
You should be using $chr()'s equivalency of these characters in your script to make it clear, $chr(2) is bold etc, you can use $asc() to get the ascii number of these characters, but here is the list:
2 for bold - control + b
3 for color - control + k
15 for 'stop' - control + o
22 for reverse - control + r
29 for italic - control + i
31 for underline - control + u
Use that in your script.