Hmm, they show up for me [1]. That screenshot is an HTML file but I also looked at JS, Python and Markdown and all were showing syntax highlight in diff commits.
Thank you for clarifying. I'm not sure why I didn't initially associate 'syntax highlighting' with what it is. I can see how this would be useful when dealing with a lot of information, especially when reviewing another's work.
You can't claim that Bitbucket has syntax highlighting and then post proof that isn't actually proof. Well you can, but why bother?
I just checked our Bitbucket. There's no syntax highlighting for any of our used languages for diffs. There is no option to enable or disable it. When you do a search for it, it's still an open issue in BitBucket's public issue tracker[0].
If you've got some wizardry working that isn't an external script, hook it up.