For some reason I have never thought to apply this to my PR comments. I had been using tags like #question on a comment, but not emojis. I tend to forget to use those and thought there might be a better way. I found this nice document from github user raorao which relays what I was thinking about. I have since tweaked it a little to fall in line more with the gitmoji.dev definitions.
Here is a key to my PR comment emoji usage:
😻 - :heart_cat_eyes: Compliment to code/idea/etc
♻️ - :recycle: Non-blocking proposed refactor
➕ - :heavy_plus_sign: Non-blocking proposed addition
➖ - :heavy_minus_sign: Non-blocking proposed removal
❓ - :question: Non-blocking question
⚠️ - :warning: Blocking comment that must be addressed before PR acceptance
That is it, you could argue that the ➕ and ➖ could just fall under the ♻️ emoji, which I won't disagree with, but do with this what works best for your environment and team.