Animated Emoticons
Related to BUG: 463369, animated emoticons aren't supported - which sucks because they're widely used across the Fediverse.
Unfortunately looking into the issue yielded that it's just not supported by Qt. To display custom emotes, we use html img tags and Qt's built-in HTML support but it only supports basic, non-animated images. GIFs only show one frame and it's static.
Qt's animated images use QMovie internally to handle playback, where Qt's rich text nodes doesn't. Fixing this would mean either submitting patches for Qt to handle animated images, or redo-ing how we display emoticons in the first place.