I don't know if they still do it, but at the time Twitter charged money to display user avatars in a larger size, and styled as a hexagon. I think they were NFT tie-ins or something? They were difficult to ignore, so I wrote a snippet to turn hexagons back into circles.

[edit]: https://news.ycombinator.com/item?id=30012904 ("Twitter Rolls Out NFT Profile Pictures")