Hey Jeff, I just got a response back from Marketo. This was their answer.
Thanks,
Justin
ICS files are incredibly simple creatures, they don't have any way of holding font/formatting, etc. As a result, Outlook looks for specific things to control formatting. One of the key things it looks for is a colon followed by a hard enter. Anything following :
Ends up being bolded and blue.
I went back through the .ICS file and changed :(enter) to -(enter) and the ICS file now has all the funky blue/bold stuff removed. I also had to change the token for Phone: because the colon(enter) after Phone was also causing problems.