Hi there,
I personally think that this a forum, and forums are places to discuss things about CubeCraft with others that play CubeCraft. There are already ways you can interact with a posting, such as replying to it, quoting it, liking it, adding your opinion in the poll (if there is one). Though I get where you might be coming from.
If it’s only an emoji you want to respond with, and there’s nothing else you want to say, this could be quite useful, every now and then. They only really need a few emojis, and the Like button.
The thing people forget is that the CubeCraft Forums run off an open-source forum software, and this may not be a feature you can add on it (as far as I know, the forum software is pretty old). And if they were to develop it manually, it would take quite a bit of time.
Anyways, I think this might be useful in some cases, but not exactly a necessary thing to add.
Thanks for your suggestion :)