you have read it as follows: ```_``` is the separator; the left side is the version, the right side the operator. evaluation is ```operator(version, whateverversionyouwanttotest)```. in the example, ```5_>``` means ```>(5,test)``` or ```True``` if ```test > 5```. 
if you want to change it, you need to adapt configobj i think (section names can't start with eg ```>```) or change the evaluation so ```5_>``` is evaluated as ```>(testversion,5)```