As part of the Wikidata project, Jeoren De Dauw wrote an extension to prettify diffing of Javascript. It'd likely be a good addition for EventLogging to have too!
Logging as a TODO item after discussing with Ori
https://www.mediawiki.org/wiki/Extension:Diff
Example: https://www.wikidata.org/w/index.php?title=Q5589038&diff=8314580&oldid=8314578
Version: unspecified
Severity: enhancement