Issue Summary

This is reproducible on Data Center: yes

Steps to Reproduce

Enter markdown (comment or PR description) with an @-mention in a URL followed by an emoji:

This link has something that looks like an at-mention: http://localhost/@mention/

And here's an emoji: :facepalm:

Expected Results

The URL should remain untouched (but as a link) and the emoji text should be replaced with its emoji.

Actual Results

The "@mention" text in the URL is replaced with the facepalm emoji. There is nothing after "And here's an emoji:" (the emoji and the text are gone):

Workaround

None known