It looks like it's made to appear as much like non-ad content as it possibly can while still maintaining plausible deniability on your part.

We stopped advertising on reddit after the rise of the_donald and other white supremacy subs led to our ads being placed next to a lot of bigotry and white supremacist content, even in subreddits you'd generally consider innocuous. The hate groups have spilled over into most subs now.