I think that's now removed no? Or at least, I haven't noticed it for a while.
I got hit with the Google hammer regarding a similar banner, where they threatened to stop indexing the site completely, so I assume they had a similar message. Or maybe they're large enough to be exempt. I don't know.
It's a small banner on Reddit's AMP pages. Once you click "view more comments", you're taken over to the mobile version which has the huge banner.
Shamless plug: you can see this behaviour in the two screenshots in lower left corner in this post https://grumpy.website/post/0PhBPyfR- Reddit redesigned the AMP page to include some comments, but the behaviour is essentially the same.
You have to be logged in and toggle a preference to disable the popup. But then it forgets I'm logged in and I see it again. I agree that it's extremely obnoxious and has just resulted in me never bothering to look at Reddit on a phone anymore.