In short: Google Discover is getting ads once again. According to a couple of users on Reddit, they are seeing ads in the Google Discover feed, and this is the second time that Google has been testing ads in Discover. It had tested them in Discover in the past, this time they have opted to redesign the ads and now it is A/B testing them once again. It's a test, seeing as very few people are seeing these ads in Google Discover. It's important to remember with tests that these features may never actually make their way out of the test and over to your device.
The screenshot that surfaced on Reddit shows the ad, which does look a bit different than the rest of the news articles in the feed - though not much different. There's an "ad" badge before the title, similar to what you would see in search results from Google. There is also the three dots icon for the menu, which would likely allow you to give Google feedback on the ad - whether it's appropriate, relevant, etc. Similar to the other cards in Google Discover. It fits in rather nicely, and many people may not even notice that it is an ad. Which could be an issue for Google down the road. Though right now, this is still in testing so it may change before Google rolls it out.
Background: It's important to remember with Google and its products, that it is just a way for Google to show you more ads. While Google has been working to diversify its revenue streams in the past few years, it still gets over 95-percent of its revenue from advertisements across the internet. And all of its products work to show you ads, some are more discreet than others, but that is the whole reason behind them. So seeing ads from Google in Discover should not be a surprise. In fact, the surprise should be that it took Google this long to add ads to this feed, seeing as it was the Google Feed before Discover and Google Now before that. So it's been around for about six years now.
Impact: No one likes ads, we know that. But ads are what help to keep the internet as open as it is. If it weren't for ads, many websites would be behind paywalls, as these websites are not free to operate. Ads are essentially a necessary evil for the internet to continue operating. And if you don't like Google putting ads into its services and products (like Gmail, and now Google Discover), then you're going to want to use other products and services, and that might just mean using an iPhone, unfortunately. While ads are only in testing on Google Discover, it is very possible that these will be coming to Google Discover across all Android smartphones in the very near future, just as it did Gmail. It took Google nearly eight years to bring ads to Gmail - particularly the Gmail app - but they finally launched, and they aren't as annoying as other ads on the internet.