In your a11y settings would it be possible to decouple "allow animated images and emoji" into 2 separate settings like "allow animated images" and "allow animated emoji"?
Usually I'm fine with animated images but I have a real issue with animated emoji. In particular the popular party parrot emoji instantly does something weird to my eyes and makes feel sea sick. It's literally like a feeling of nausea in my eyes and brain. I have to immediately look away if I see that. I was really happy when I discovered Slack's a11y settings! The only downside is that I miss out on animated gifs.
Have you had any other people report issues with emoji like the party parrot ones? I feel like those in particular are potential seizure risks because they quickly flash and rotate. Google "WCAG seizures" for context.
I personally also have a similar adverse yet less extreme reaction to some horizontal slide transitions common on many websites especially when those happen automatically without my interaction.
Going further in regards to Slack I personally would even love having the image setting be like "autoplay animated images" so that I could disable that but still play them as desired. Basically require click to play like how videos work.
Thanks for taking the time to read all this and for making an awesome product! Feel free to reach out for more info.