I have made some mods to Electrum in order to make it display thousands separators in numeric monetary values. When I first mentioned the idea of adding thousands separators (commas) people seemed just against the idea of using commas but instead wanted to use some other symbol as a thousand separator. The changes use the system's settings to determine what thousand's separator to use. It has been tested on Linux only for now. You can download the source at:
https://github.com/shawnpringle/bitcoin-electrumThe changes are based off of 1.8. You can run it from source if you get the python interpreter and its libraries. It is meant to be both platform and culture agnostic even handling numbers which are different in Egypt for example.
It's fun hacking the GUI.