Also, please no "tHiS iS eNgAgEmEnT fOr rEdDiT" comments. Would you rather have no such banner? As I'm not pushing anyone to become a long-term active user on Reddit, I don't see any benefit for the company from this. If you have a spare account, this may be a good cause to fire it up for a few hours.
For anyone concerned about traffic to reddit, the absolute best thing you can do is find ads next to "offensive" content and e-mail the CEOs and marketing departments of those companies saying you won't use those products due to their ad placement on reddit. Literally nothing else will hurt them faster.
You increase the daily/monthly active users count if they count only visiting people as well. Only by 1, but still. If they are using that number in any kind of negotiation with other companies to persuade them to do business with them (ad-related or otherwise), you probably wouldn't want to increase that number.
Not much, but it's honest work.
Edit: I'm not talking about this message in r/place in particular. I think this is awesome!