Yes absolutely. Not only are they federated, but they are even exposed via the API, as described in more detail at https://piefed.social/c/piefed_api/p/1596518/emoji-reactions-in-the-piefed-api. Of course it is up to each third-party app to decide how or whether to do anything with that, but it’s there whenever they are ready for it, and emojis show on the PieFed web UI.
See also https://codeberg.org/fediverse/fep/src/branch/main/fep/9098/fep-9098.md e.g.:
This document is based on implementations of custom emojis in Pleroma, Mastodon, Misskey and Fedibird.
That said, I am not certain if they can all interrelate currently, as opposed to merely representing similar ideals. This should help get you started if you wanted to do more deep diving though:-).
Tuuktuuk@nord.pub 2 months ago
…kinda?
They do federate, so that I can see reactions from other PieFed instances just fine. But Lemmy does not use the data for anything. It just passes it on for whoever can use it.
Martineski@lemmy.dbzer0.com 2 months ago
I was asking specifically about other “platforms” besides piefed because I’m curious how supported are emoji reactions across the fediverse. I had around a year of break form the fediverse so I’m a bit ootl on recent developments.
Tuuktuuk@nord.pub 2 months ago
I am fairly certain no other platforms support them at the moment.