InfoPath Dev

I'm finding something I need to double check out with you guys, because I don't have access to the files now (they were deleted) 

We all know that xml is case sensitive.

Scenario - let's say we have an original form submitted, with the filename being "Smith-John_20130102" (concatenated on submission)

 Then, someone opens the form, they change the names so that it re-concatenates saves it back with the name "SMITH-JOHN_20130102"

Will that save as a duplicate file in the form library?

 This is a great question - I'm not sure. I don't know if SharePoint is case sensitive when it comes to overwriting - set up a quick test form and library - display the field you use for your filename on the form so you can manually change the casing and see what happens.