Ok, so we had a bunch of emojis in our database that weren't delimited with a : so they were called things like red instead of :red:. It didn't cause an issue until we upgraded to 1.6, because inline emojis were not available in the version we were running.

So when we updated to 1.6 (around 6 hours ago), there was a window of about 3 hours, where text in posts and comments that mentioned any of those undelimited emoji names, would get replaced with the emoji (but only on our instance). We updated the emoji list to delimit them properly, and it is no longer occurring on new content. Existing content posted or edited during the period where we had the undelimited emoji on 1.6 will continue to show the emoji, but posts made before or after that window are fine. There's no way for us to identify or push a fix to the posts that made it through, though if any of them belong to you, you can edit the post, which will fix it.