I dont see how that's neccessary, considering there is no way for a number to be lower or upper case. The help file says:
isupper - text contains only upper case letters
So im really not sure why it's not working. Like i said, it works fine for me.
Also, both synth7's and MikeChat's scripts are missing the $nick in the kick command. Should be: kick $chan $nick Suspected Virus-Drone.
EDIT #2: Ok Mike, now I see what you mean. Since in the user's quote the knick had a ` in front of it, i guess that could complicate things.
So yes, the isalpha is needed. Just remember to fix the kick command like i said above. Sorry about that Mike.