Recommendations for future contributions to the code base

Python

Follow Python style naming and comments, don't invent your own naming scheme, see PEP-8
avoid cyclic module dependencies
avoid global state variables
test for multiple browsers and input formats
avoid comments that repeat what the function name should say anyways, instead try to find good, self-documenting names for functions, classes and modules
avoid Java-isms, there is no need to have a class for everything and there is nothing wrong about putting multiple small classes into a single file
if you do nothing in a an exception handler except re-raising the exception you can as well omit the except clause, finally can stand by itself

Javascript

when writing your own Javascript modules in a separate files always your functions in a namespace, using the !!!! Placing them in the global namespace will only mean an endless sea of pain
don't go wild with the Javascript libraries, simpler and less dependencies is usually better
don't assume URL's in Javascript files, this makes it much harder to change and adapt to different environments
check for null or undefined, not doing so can lead to weird website behavior

Data

avoid redundancy at all costs
think long about which information to store in the graph and which in the relational database, don't store it in the graph just because you can, but for the cases when it is the more effective model for the data