@Simon – can you provide a sample indd file with a PDF and an IDML file as well of one single page of your report. No need for images. Just one page. Maybe there are other things at play here. Together with the set "Ligature" feature. Not only one culprit, but two or more factors…
Maybe a IDMS snippet will do as well for testing, but I'm not sure about this. Better provide an InDesign file. As I already said, one page should be enough.
@Sairus – I don't know, if this would qualify: I see this subtle effect on thinning in rendering as well.
But I'm on Mac OSX 10.7.5 with InDesign CC-2014 opposed to your OSX 10.9.4. Could this make a difference?
In my tests two ingredients are needed to force this effect on Chrome's rendering:
1. Set the feature Ligature
2. Have a ligature in the text
With just a lorem ipsum text (no ligatures there) all went good. No effects visible.
And this result is leading me to the conclusion, that there must be more than the "Ligature" feature turned on to force that effect. So I'd like to see some of the original formatted text of Simon.
Uwe