Post about Microsoft pinned as announcement

Why am I seeing a post about Microsoft from 9 days ago pinned as an announcement at the top of /all ?

4 comments

If I understand correctly then it's pinned on the community and not the instance and it just happened to be at the top of your feed.
- Oh... I just checked and it is actually pinned on the instance. Lol
  
  Apparently it was done by a mod and not an admin which is even weirder.