I tried DDG for a while (a month, but probably a year ago now) but found I was always doing "!g <search terms>". So I just went back to using the address bar for searching and just the standard FF shortcuts (called "search engine keywords" IIRC) + a few extras I've added over the years.
On Firefox I have
g - google
ddg - duckduckgo
yt - youtube
w - wikipedia
etc.
easy to type without the bang at the front (Google and Wikipedia are defaults, not sure what the other ones are). I gather on DDG you can use them at the end so you need the ! as a delimiter.
You don't have to load the site (trivial, but not negligible), throwing a bang in front of an already written search is simpler than rewriting the search, and google doesn't build a profile around you as another entity is doing the search.
He means that, for example, "!hn rust" would search hacker news directly for rust, whereas "hacker news rust" on google would do a similar job but via google, informing google of your search.
Sorry, ripdog and icebraining - I got it wrong. I hadn't played with ddg for a while and my memory was in error - I recalled !g returning google results in the ddg interface. My mistake.
I couldn't correct it because of HN's stupid 5-comment policy that applies to comments made in all threads combined, and couldn't edit the original comment with a correction as it had been more than an hour. :/
That's definitely not what his comment says. He's quite clearly talking about !g (not other bangs) and saying (incorrectly) that another entity (DDG) is doing the Google search so Google can't build a profile around you.
A few of the ones I abuse constantly:
!g - google
!bi - bing image
!yt - youtube
!so - stackoverflow
!w - wikipedia
!py - python docs
The exhaustive list is here: https://duckduckgo.com/bang.html