Someone recorded this back on that evening of "position: fixed" and what a memory:

they should unban position: fixed. for funsies.

It seems that the Choost post is going around, and people are experiencing it for the first time. So here's an explanation for anyone that comes looking for it.

If you've ever looked in the markdown cheatsheet and seen that position: fixed is not allowed, you might not realise that it was allowed at one point. Back in t' day, you could use it to position elements outside of your post, and even have them remain on screen after you've scrolled past the post. This is obviously ripe for abuse in the long-term, and was removed in July 2022 (then more fully in November) bringing about a new age of posting.

Posts that were made before this change, however, still function. There just aren't that many. Off the top of my head there's One World Story, the little dog friend, an earlier post from @mog and, of course, Choost:

https://cohost.org/mog/post/11366-choost

If you've started seeing the logo change to Choost, it's because you scrolled past that post. If it bothers you, you can silence it up in the meatball menu ••• in the top right ↗️ of the post. Don't be afraid of silencing a post, you can always unsilence it later via your user settings.