Bitbucket has full Unicode support in all text fields, which should cover most emoji needs. You can use actual emoji characters in commit messages, Pipelines step names and commands. (Note that the latter will require your build container to support Unicode properly - we have an open issue around this with our default container.)
We won't be adding chat-style text emoji (like :awesome:) support to Pipelines for the foreseeable future, as there are other high priority tickets we're working on instead. So I'll close this as "Won't fix" for now.