This issue with webmentions and emojis is the reason when I manually set each slug, because what I was finding was that my posts were not pinging. However, when I used the permalink then it worked. For example:
https://collect.readwriterespond.com/?p=10116
Rather than:
https://collect.readwriterespond.com/No+webmentions+to+original+URLs+that+include+emojis