Email processor silently truncating anything after an emoji in inbound emails
For those looking for a workaround for this issue, we created a tiny extension called Multibite which replaces unsupported multi-byte characters with the Unicode replacement character (or any other character, depending on configuration). We did not want to pollute core with this code as the goal should be to support utf8mb4, after which the extension becomes obsolete.

I should note that we aren't running this in production yet, so it hasn't seen much real-world testing.