The point is that with the long variable names, often times half or even more of the total diff-json-string sent is variable names. Of course one has to use all the optimizations there are for network traffic -- for example by sending through websockets -- but cutting down variable name length in a non-debug version seems like an important step.

Also, we have started to save files in the JSON.stringify one obtains from this, rather than the "outerHTML", which wouldn't preserve sibilign text nodes and alike. If variable names are longer it means that the file size increases rather dramatically.