What behavior do I expect? I expect it to not throw an error. I expect whatever string I give to be inserted into the widget unadulterated (ie: if I give the string "foo {" I expect to see "foo {" in the widget). 

Tkinter is effectively telling me "you have a Tcl syntax error". Since I'm programming in python I should be insulated from that, particularly since the error comes internally after Tkinter transforms my data. 

How Tkinter does it under the hood, I don't care. Tkinter should make sure that the data it passes to the Tcl interpreter is well-formed.