We actually have an entire document in Confluence specifying which ones to use, for which reactions

Well I guess that stops ambiguity. There was a discussion here about people taking emojis the wrong way. Get ahead of the problems I guess.

I stopped using thumbs up, and started using check marks to acknowledge its done or I know.

You should copy your work and put out a reference webpage. I don’t think many businesses are as far ahead as you I would think.