On a Slack workspace where there are custom emojis with non-ASCII characters (in my case: `:giàfatto:`, `:èinaccettabile:`), they are displayed correctly:

- in the emoji/reaction picker (filter and selection work fine)
- in the emoji completion dropdown (prefix filtering works fine)

but not

- in the message body (they remain unexpanded)
- in the reaction "button/count" itself (the button is displayed with the reaction count, but instead of the image the first characters of the emoji name are displayed)

Slack: custom emojis with non-ASCII names aren't displayed