GitHub also adopted it, and I would say it depends on the platform and target.

For a developer platform I find this unprofessional, but for traditional chat systems it might be useful if you quickly want to go through lots of messages and get a first impression about what the community thinks about topic X.

On Lemmy I would prefer emojis to up and down votes, the reason is that people often do not bother to explain why they up or down voted it.

I would argue, overall, that adding it puts maybe a bit more pressure on the server for no actual benefit.

I overall would like such a feature here on Lemmy but only if there are limits how you can use them, I speculate some people would constantly add and then remove them with might cause some more traffic and pressure on the server, so there should be a limit. Unregistered people should not be allowed to add reaction or use them, only one reaction per post or within x hours… and such limitations.