Firefox and Google Chrome probably have the equivalent of many small high quality libraries embedded in them, implementing 'business' logic or protocols, that could be reused in more places.
I guess a large scale study on github could be done, with a graph analysis to show potential "cut off" points in codebase.
It’s a bit telling that they linked to the GitHub repositories rather than specific lines of code they were talking about.
To me it looks to be trying to uphold your anonimity until you commit (click) through to the site/link. But certainly other ways they can approach this if it really bothers people.. I'd prefer DDG doing the lookup.. or having no fav icons.. over my computer going and downloading all my bookmark or other source icons
Maybe this should be an opt-in rather than an opt-out feature?
Edit: as pointed out by warpspin in another comment, this is about the DDG Browser, not search results.
This is mostly a UX issue IMO.