Is this optional? I would personally have no interest in writing such emails - it's just more work.
They also made it fun. One manager conspiratorially told me were two schools of thought around what made a great shipped email; copious footnotes or funny gifs, and jokingly told me to make sure I had one or the other or even better both.
Stripes love their "footnotes" though, which are essentially links to things. Even though everyone had full HTML email, they were almost always formatted in the style of Hacker News[0] comment links. The people at the top can definitely set the communications tone for the rest of the company.
That doesn't sound optional at all.
From my point of view, making things fun isn't fun. Watching a comedy routine is fun. Writing one isn't.
Driving a car is fun. Building a custom hotrod isn't.
Going to the museum is fun. Learning to paint isn't.
Playing a video game is fun. Writing a video game isn't.
Going to a concert is fun. Playing a gig isn't.
Eating is fun. Gardening isn't.
Oh, wait, none of that is universally true.
I strongly doubt it was optional, if you wanted a positive career trajectory.
This is also the case in most other companies - it's just that different firms have different expectations for how their employees should market their accomplishments.
However if all the threads are just “great job on X!” I can see how that could be low-value self promotion.
I worked for a company that did cards, like thank you cards, or well done cards that you could give a colleague and these would get handed out each month to the recipients. It made me cringe. Can't believe people are so needy.